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 Pteris, Dryopteris and Pteridium (Fern).                                                                                                         

Systematic position

Kingdom          –        Plantae

Sub kingdom     –        Embryophyta Phylum            –        Tracheophyta

Class               –        Leptosparangiopsida

Order               –        Filicales

Family             –        Polypodiaceae

Genus              –        Pteris, Dryopteris, Pteridium (For Rajasthan PMT & UP CPMT Students Only)

1. Habitat : Ferns live in moist, cool and shady places. They are perennial and evergreen. Fern Dryopteris filix-mas is commonly known as Beech fern or Male shield fern or Hay

scented fern. There are about 150 sps. and 25 sps. have been reported in India. It is found in sub-tropical regions as well as warm temperate regions.

(2)Structure

1. External structure : Fern plant is sporophytic (2n) with an underground rhizomatous stem, large aerial leaves or fronds and adventitious roots. Rhizome is sparingly branched in Dryopteris, moderately branched in Pteris and Adiantum and profusely branched in Pteridium. Young leaves show circinate ptyxis. Younger parts of leaves and rhizome are surrounded by brown hairy structures called scales or ramenta. Leaf bases are persistent. Leaves are pinnately compound unipinnately Pteris

Rachis

Pinnae

Young leaf with circinate ptyxis

Adv. roots

Petiole Persistent

leaf bases      Sori    Vein

Rhizome

1. (B)

vittata, incompletely bipinnate Dryopteris filix mas, bipinnate in Pteris, biaurita, Dryopteris rigida, tripinnate in Pteridium aquilinum. The leaves show open dichotomous type of venation.

(ii)Internal structure

Fig : Dryopteris (A) Plant showing habit

2. Fertile pinnule

Epiblema

1. Root : The epiblema is provided with unicelled root hair. It followed by thin walled outer cortex. The inner cortex is thick walled (lignified). The cortex is followed by endodermis with characteristic casparian strip. The pericycle may be 1-2 cells thick. It is also made up of thin walled cells. The xylem is diarch and exarch with two phloem groups alternating the protoxylem.
2. Rhizome : It Pteridium aquilinum the epidermis is followed by sclerenchymatous hypodermis and the thin walled ground tissue. The young portion has a siphonostele, but this later forms two concentric cylinders of vascular tissue. The outer ring corresponds to a dictyostele (e.g. Dryopteris and Pteris) or dicyclic or polycylic dictyostele

Outer cortex

Inner cortex

Endodermis Pericycle Metaxylem

Phloem

Protoxylem

Fig : T.S. of Dryopteris root

(e.g., Pteridium) which is distinguishable into small meristeles. The inner ring comprises generally two medullary meristeles. The two rings are separated by two patches of thick walled tissue. Each meristele has its own endodermis followed by thin walled pericycle. It is amphicribal (ectophloic) with mesarch xylem.

The phloem lacks companion cells. In Dryopteris filix-mas the vasculature comprises a dictyostele consisting of a ring of meristele. In Pteris, however, the vasculature ranges from solenostele to polycyclic dictyostele.

Rachis : The epidermis is followed by thick walled hypodermis. The ground tissue is thin walled. In Pteridium aquilinum several meristeles lie irregularly scattered in the ground tissue. In Dryopteris filix-mas there are 6–8 meristeles arragned in a horse-shoe like manner and single arched with hooked xylem in Pteris. The structure of the meristele is similar to that of rhizome.

(d) Leaf lamina : The pinnule of Pteridium aquilinum shows distinct upper and lower epidermis. The lower epidermis is provided with stomata. The mesophyll is differentiated into an upper zone of palisade parenchyma and a lower of spongy paranchyma. The spongy parenchyma has large intercellular spaces. The vascular strands lie embedded in mesophyll. Each strand is generally amphicribal with its own endodermis and pericycle but sometimes they are bicollateral also. The bundles in minor veins are collateral.

Upper Epidermis

Phloem

Xylem

Glandular cell

Fig : Dryopteris (A) T.S. rachis (basal portion)

2. T.S. rachis (Upper portion)

Lower epidermis

Stoma         Bundle sheath  Air space

Fig : V.T.S. of pinnule or sterile leaflet (leaf lamina) of Dryopteris

(3)Reproduction

1. Vegetative reproduction : Vegetative reproduction can occur through fragmentation or rhizome and adventitious buds and these on separation

gives rise to new fern plant.

2. Sexual reproduction : Sexual reproduction takes place through spores. Spores are born in sporangia. The spores are of one kind only (homosporous). When leaves are mature they bear groups of sori on the under surface of fertile pinnae. Such fronds are called sporophylls. The sori are borne in two rows on two sides of median vein of pinnule in between the margin and the midrib.

Sori are linear and submarginal in Pteris

Sori (a)

Upper epidermis

Mesophyll      Vein

Lower epidermis Spores (haploid)

Sporangia (stalked)

Covered indused (membranous) (true indusium)

Placenta

(b)

Fig : Dryopteris (a) Part of sporophyll with sori

(b) T.S. of sorus

and Pteridium and median abaxial in Dryopteris. Each sorus is surrounded by a kidney-shaped covering called indusium. In Dryopteris, true indusium is present because this arises from placenta or placental tissue, from which sporangia arise. (In Pteris false indusium is there because it is formed by leaf margins).

In sorus of Pteridium is covered by two flap like appendages that protect the sporangia. The upper flap is called false indusium and lower is called the true indusium. In the centre of sorus, the vein ends into placental tissue from where arise a number of sporangia. The sorus is mixed in Dryopteris (i.e., no definite arrangement of sporangia).

Sporangium : The sporangial development is leptosporangiate i.e., it develops from a single superficial initial. (In eusporangiate type the sporangium arises from a group of initials.)

A sporangium is distinguishable into a stalk and a capsule. The stalk is multicelled and biseriate. The capsule is oval or elliptical and biconvex in

shape. It consists of a single layered wall followed by double layered tapetum that encloses the archesporium. The archesporial cells divide and redivide to form a mass of sporogenous tissue. Most of the sporogenous cells behave a spore mother cells. They undergo meiosis to form tetrahedral tetrads of (haploid) spores. As a result 32–64 spores are formed in each capsule. The tapetal layer is nutritive. It degenerates at maturity of the sporangium.

Stomium

Spore

Spores Stalk

At the capsule matures, about four lower median cells of the jacket

Fig : Dryopteris – One sporangium

stretch tangentially. Of these, two median ones identify the place from where the capsule opens. This is called stomium. The remaining cells of the same median row of the jacket covering about three fourths of the perimeter become specialised.

They develop a thickening along their radial and inner tangential walls. This layer is called annulus. At maturity the inducium dries exposing the sorus. The cells of the annulus loose water. Due to presence of thickening along the radial and inner tangential walls, their upper walls contract and the inner ones straight and the annulus coils. Thus, it exerts pressure on the wall resulting in breaking of the capsule between the cells of stomium thereby releasing the spores.

Gametophytic generation

1. Spores :   It is the first cell of gametophytic

generation. Spores are double layered. The outer wall exospore is much thicker than inner endospore. On approach of favourable condition spore germinates to form a filamentous gametophyte which develops into green and heart shaped prothallus.

2. Prothallus : It lies flat on the soil surface, attached by means of numerous delicate rhizoids. The fern prothallus is single celled thick. Although at maturity, the portion below the notch becomes many celled thick, i.e. cushion. Prothallus shows polarity and dorsiventrality. The dorsal surface is smooth and the ventral is provided with

Apical notch Cushion

Archegonia (upper side and neck points downwards)

Antheridla (lower side)

Rhizoids (unicellular)

Fig : Mature prothallus of Dryopteris

unicelled rhizoids and sex organs. Diameter of fern prothallus is 5 or 6 mm to 13 mm and each cell of prothallus is having single nucleus and many discoid chloroplasts.

Fern prothallus is monoecious but protandrous (antheridia mature first). Antheridia are present in between the rhizoids while archegonia are present near the apical notch.

• Antheridium : It consists of a three celled jacket enclosing a mass of androgonial cells. The two lower jacket cells are ring like (first and second ring cells), and the terminal cell is called as opercular cell or cover cell or cap cell. Sometimes, there may be two cap cells and in that case the jacket is four celled. The last generation of androgonial cells forms the androcytes. There may be 20–25 androcytes in an antheridium, each of which is metamorphose into a spirally coiled, multiflagellate antherozoid.

Spermatocyte

Fig : Dryopteris (a) L.S. antheridium (b) dehisced antheridium

3. Multiflagellate spermatozoids

• Archegonium : It is a flask-shaped structure having venter and neck. Neck is projected out of the prothallus and is curved posteriorly. Venter is having basal large egg cell and upper small venter canal cell. The neck is having single neck canal cell but is binucleate. Venter is not having any covering or jacket but neck is surrounded by jacket of 4 ventrical rows of cells.

Prothallus cells

Oosphere

Neck

(a)

Ventral canal cell

Binuclete neck canal cell

Mucilage (b)

Fig : Dryopteris (a) Mature archegonium

2. Before fertilization

3. Fertilization and development of sporophyte : Before fertilization the walls of androgonial cells disorganise to form a mucilagenous mass. The opercular cell is removed when it comes in contact with external water. The neck canal cell and the ventral canal cell degenerate. The cover cells split apart giving a free passage to incoming antherozoids. The antherozoids are attracted by chemotactic stimulus which is probably provided in the form of malic acid. A single antherozoid is able to fuse with egg to form zygote (2n), which is beginning of sporophytic generation. Zygote divides first by vertical division, followed by another vertical division and quadrat stage is formed. Then octant stage is formed by transverse division. The foot and root develop from four hypobasal cells and cotyledons as well as stem develop from epibasal cells and thus sporophytic plant is formed. At maturity foot is hemispherical mass of gametophyte from which it absorbs food. Generally a single sporophytic plant develops from single gametophyte or prothallus. The fern sporophyte is initially dependent upon gametophyte but later on becomes independent.

The life cycle is diplohaplontic with heteromorphic alternation of generation.

Adventitious bud

Fragmentation

Vegetative reproduction

Embryo Oospore

Fern plant

Sporophytic generation

Sporophyll

Sorus

Fertilization

Oosphere Sperm

Archegonium

diplophase (2n)

Gametophytic generation haplophase (n)

Sporangium

Spore mother cells

Meiosis

Antheridium                                      Spores

Prothallus

Fig : Graphical representation of life cycle of fern

 Selaginella.                                                                                                                                                             

Systematic position

Kingdom          –        Plantae

Sub kingdom     –        Embryaphyta Phylum            –        Tracheophyta

Class               –        Ligulopsida

Order               –        Selaginellases

Family             –        Selaginellaceae

Genus              –        Selaginella (For MP PMT Students Only)

1. Habitat : Selaginella is commonly called the little club moss or spike moss and is having about 760 species, out of which 70 species have been reported from India. Selaginella is mainly found in damp shaded places. A few species are xerophytic and can withstand the dry conditions for months together. In dry conditions, the plant rolls up into a compact ball and root system is disorganized. During the rainy conditions the ball on absorbing moisture, becomes green again. Such plants are called resurrection plants or bird's nest moss, e.g., S.lepidophylla, S.bryopteris (Sanjeevani) and S.rupestris (ornamental).

The epiphytic species grow on the branches and trunks of moss covered trees. The common epiphytic species are S. chrysocaulos, S. kraussiana, S. oregana, S. chrysorrhizus.

(2)Structure

1. External structure : The plant body is sporophytic (2n), which is an evergreen and delicate herb having adventitious roots. The plants show great variation in their morphology. Some species are prostrate growing upon the surface (e.g., S.kraussiana), some are suberect (e.g., S.trachphylla) and others are climbers (e.g., S.allegans). Plants are many meters long in S.willdenovii and only few centimetre long in S.spinulosa. The stem is covered with four rows of small leaves, out of these two rows are of smaller

leaves and two of large leaves species with

dimorphic leaves such as S.kraussiana, S.helvetica, S.lepidophylla, S.chrysocaulos etc. are grouped in

Fig : Selaginella kraussiana : (A) General habit (B) A part of the plant

3. Small portion of (B) showing arrangement of leaves

subgenus heterophyllum. Species having leaves uniform in size are grouped in the subgenus homeophyllum. These species are S.spinulosa, S.rupestris, S.pygmaea and S.oregana etc.

Leaves are sessile, ovate or lanceolate with acute apex. Unbranched midrib is present in the centre of each leaf. The leaves are ligulate, i.e., a flap-like outgrowth is present at the base on adaxial side called ligule. It may be fan-shaped or tongue-shaped or lobed or fringed. At the base of ligule, there is present a sheath of elongated cells called glossopodium (secretory).

The leaves possess a midrib but there is no venation. At the place of bicuraction of stem, a leafless, colourless, positively geotropic, elongated, cylindrical structure grows downwards. This is called the rhizophore and is quite different from the root in that it has no root cap. Rhizophores are not present in S.cuspidata. Rhizophores typically develops of adventitious roots at its apex.

(ii)Internal structure

1. Root : The root is distinguishable into a single layered epidermis having root hair. This is followed by a 3– 4 layered thick walled hypodermis representing outer cortex. The inner cortex is thin walled. The endodermis delimits the cortex. It is generally not distinct but in S.willdenovii it is very clear. The endodermis is followed by 1–3 layered pericycle. The stele is a protostele. It has a central core of xylem surrounded by phloem which is horse shoe shaped. It has a single protoxylem element (monarch). The xylem is exarch.

2. Stem : The stem is internally distinguishable into a single layered epidermis having no stomata. This is followed by cortex. The outer cortex is thick walled (hypodermis) followed by thin walled inner cortex. The hypodermis is very well developed in xerophytic species. The stele is suspended by unicelled (rarely multicelled) trabaculae (modified endodermal cell). This layer, due to presence of casparian strips is regarded as endodermis. The stele is a protostele (haplostele) surrounded by a pericycle with a central core of xylem enclosed by phloem. Protostele is diarch and exarch.

Root hair

Epiblema

Cuticle

Epidermis

Cortex

Pericycle

Fig. T.S. root of Selaginella

Hypodermis Cortex Metaxylem

Pericycle Protoxylem

Endodermis

Phloem

Fig. T.S. stem of Selaginella

Protoxylem Metaxylem Phloem

Endodermal trabeculae

Casparian band

Xylem

3. Leaf : The leaf displays a simple structure. It is distinguishable into upper and lower epidermis enclosing mesophyll tissue in between. The upper and lower epidermal layers are 1-cell thick each. The lower epidermis is provided with stomata. The mesophyll is uniform, being composed of elongated chlorenchymatous cells with large intercellular spaces. Each measophyll cells has one (S.martensii), two

(S.kraussiana) or eight (S.willdenovii) chloroplasts. Each

Cuticle     Xylem       Chloroplasts

Upper epidermis

chloroplast  has  several  pyrenoid-like  bodies  similar  to

Lower epidermis

Stoma

Phloem

Air space

Anthocerotales. The single midrib bundle is concentric, amphicribal (ectophloic) with annular or spiral tracheids surrounded by a few sieve elements.

Bundle sheath

Fig : V.S. of leaf of Selaginella

4. Rhizophore : The anatomy of rhizophore is almost similar to root. The epidermis is cutinised and it is followed by cortex. The outer cortex is thickwalled (hypodermis) whereas inner one thin walled. The innermost layer of the cortex is endodermis which is followed by pericycle. The stele is a protostele. The xylem is exarch with several protoxylem groups. In S.kraussiana, centroxylic condition (having protoxylem in the centre surrounded by metaxylem elements) has been recorded.

3. Reproduction : Reproduction takes place by vegetative and sexual (by spores) method.
   1. Vegetative reproduction : It is of rare occurrence and may takes place by following methods :

1. Fragmentation : It occurs during very humid conditions. Some branches act as adventitious branches, which get separated from the plant and give rise to new Selaginella plants, e.g., in S.rupestris.
2. By resting buds : In some cases, terminal leaves get overlapped and become fleshy and form resting buds, which are means of vegetative reproduction, e.g., in S.chrysocaulos.
3. By tubers : In S.chrysorrhizus, some branches penetrate into substratum and at terminal ends swell to form tubers, which give rise to new plants.
4. By apogamy : In some cases, development of sporophyte occurs directly from gametophyte without intervention of sex organs, it is called apogamy and such plants are genetically haploid.
   2. Sexual reproduction : The reproductive structure in Selaginella is strobilus or spike. It is a sessile structure and develops at the terminal ends of the branches and its length varies from 1/4^th of an inch to 2–3 inches in different species.

A strobilus is having many ligulate sporophylls arranged in cluster, each bearing a small, short, stalked sporangium on its upper surface. The sporangia are of two types :

1. Megasporangia : Borne on megasporophylls. Megasporangium is pale greenish and contains chalky white, yellow or orange megaspores. The megasporangium is four-lobed structure with a 2-layered jacket, one layer of tapetum and a large number of microspore mother cell. However, only one megaspore mother cell is functional. After meiosis it produces 4 megaspores out of which 1–3 may degenerate. In S.rupestris, there is only a single megaspore.
2. Microsporangia : Borne on microsporophylls having a large number of small spores. Thus Selaginella is heterosporous. Microsporangium is pale yellow, oval or

spherical body, with 2-layered jacket, one layered

tapetum and a number of microspore mother cells which undergo meiosis and form haploid microspores.

The main body consists of a wall having two layers, inside which are present numerous small microspores (400–2000). Development of sporangium is of eusporangiate type.

In most of the cases, the strobilus or spike bears two types of sporophylls; the lower are megasporophylls and the upper ones are

Microsporangium

Microsporophyll Megasporangium

Megasporophyll

Megaspores Megasporangium

Megasporophyll

Microspores

Microsporangium Microsporophyll

Central axis

Ligule

microsporophylls. In S.kraussiana there is single megasporophyll at the base of spike and the rest of upper are microsporophylls.

Fig : Selaginella : (a) A strobilus showing compactly arranged

sporophylls (b) L.S. through strobilus

In some cases strobilus contains either micro or megasporophyll, i.e., in S.gracilis and S.astrovirdis, while S. martensii and S.caulescens show intermixed micro and megasporophylls. Some sps. possess megasporangia on the ventral side and microsporangia on the dorsal side, e.g., S.oregana and S.inaequalifolia.

1. (B)

Fig : Selaginella : (A) V.S. microsporangium (B) V.S. megasporangium

3. Mechanism of sporangial dehiscence : On maturation, the sporangium splits vertically from the upper end into two valves (vertical apical splitting). The lower cup-shaped portion shrinks and the spores come out through apical slits. This is brought about by cohesion owing to hygroscopic changes in the apical and lateral part of the sporangial wall. This liberation of spores takes place at intervals in small masses.

The spores starts germinating inside the sporangium before their release; this is known as precocious germination. According to Goebel, the violent dispersal of spores is an adaptation for cross fertilization in that it helps to bring spores from different plants near each other. This is further proved by the protandrous nature of the strobilous.

4. Germination of microspore : The microspore is a double layered structure and contains oil droplets. The outer wall exospore is much thicker (spiny) than inner endospore. It measures 15–50m in diameter. The microspore on germination forms the male gametophyte. The structure and development of male gametophyte was first described by Slagg (1932). The first division leads to formation of a small prothallial cell and a large antheridial cell. The larger antheridial cell, by further divisions, gives rise to central group of four primary androgonial cells, surrounded by eight jacket cells. At this 13-celled stage (1 prothallial + 8 jacket cells and 4 primary androgonial cells), the microspore is shed from microsporangium. Each of the central groups of cells divides and redivides and finally forms about 256 spirally coiled antherozoids with two flagella (biflagellated); the jacket cells disintegrate. It takes about three weeks for germination of microspore and formation of antherozoids or sperms.
5. Germination of megaspore : The megaspore has three wall layers namely exospore, mesospore and endospore. It measures 1.5 – 5.0 mm in diameter. The megaspore on germination forms the female gametophyte. Generally the megaspore germinates inside the megasporangium (i.e., in situ). In some sps., megaspores are shed after the development of first archegonium, i.e., in S.kraussiana, while in S.apoda and S.rupestris, megaspores are not liberated till a well developed embryo is formed.

During the development of female gametophyte, the protoplasm after contraction forms a small sac-like structure. The outer wall bursts into two layers, the exospore and mesospore. At this stage, megaspore contains a haploid nucleus which by division produces many nuclei. Wall formation takes place in the upper beak-like portion

and a small-celled cellular tissue is formed. This is one celled thick at the sides and three celled thick in the middle. This is female prothallus. Some superficial cells at apex enlarge and act as archegonial initials and form the archegonia. The megaspore bursts exposing the female prothallus. Vestigial rhizoids develop.

Archegonium are sessile and embedded type and consists of very short neck having a single neck canal cell and a venter, having a single ventral canal cell and an egg.

6. Fertilization : Usually the male gametophytes are shed from the microsporangium on the ground at 13- celled stage. Here they complete their development ultimately producing spermatozoids. These are liberated by the decay of the microspore wall. If the microspore falls near the mature female gametophyte, the sperms swim from the male gametophyte to reach archegonia and one sperm fuses with egg to form zygote. Water is necessary for fertilization and sperms are attracted due to malic acid.
7. Development of embryo or Sporophyte : The oosphere after fertilization gets surrounded by wall and become oospore. The oospore (zygote) divides transversely into two cells, the upper epibasal cell which forms suspensor cell and the hypobasal cell which develops into embryo.

The embryo differentiates into foot, root, primary stem with two rudimentary leaves and rhizophore. By growth of stem and the root, the young sporophyte becomes independent of the gametophyte tissue and falls on the ground where the primary rhizophore forms roots that grow into the soil and the plant starts independent life.

In some species of Selaginella, the archegonial initial develop apogamously into embryo. In S.intermedia, no microspores are formed. Here the embryo develops parthenogenetically from the egg. In S.helvetica, the archegonia fails to open and here also parthenogenetic development of embryo is seen.

There is distinct heteromorphic alternation of generations in Selaginella.

Fragmentation Bulbils Tubers

Vegetative reproduction

Embryo

Selaginella

Sporangiferous spike

Oospore

Sporophytic generation

Microsporophyll

Megasporophyll

Fertilization

diplophase (2n)

Microsporangium

Megasporangium

Microspore

SpermatozoidGametophytic

mother cell

Megaspore mother cell

Oosphere (egg)

generation

haplophase (n)

Microspore

Meiosis

Antheridium   Male

Archegonium

gametophyte

Megaspore

Female gametophyte

Fig :  Graphical representation of life cycle of Selaginella

 Pinus.                                                                                                                                                                       

Systematic position

Kingdom          –        Plantae

Sub kingdom     –        Embryophyta Phylum            –        Tracheophyta

Class               –        Gymnospermae

Order               –        Coniferales

Family             –        Pinaceae

Genus              –        Pinus (For MP PMT Students Only)

1. Habitat : It is commonly known as pine with about 90 species among which six species are found in India. (N. East and N. West Himalayas) occurring in wild state. These are Pinus gerardiana (Chilgoza pine), P. Wallichiana (Blue pine or Kail), P.roxburghii (Chir pine), P.merkusii (Teenasserin pine), P.insularis (Khasi pine), and P.armandi (Armand's pine). In addition to these, 4 sps. of exotic pines, i.e., P.montana, P.laricia and P.sylvestris (Scotch pine) and P.strobus (white pine) have been introduced in India. P.excelsa are found at maximum height i.e. grow upto 3500 m above see level.

(2)Structure

1. External structure : Pinus is an evergreen, perennial plant of xerophytic nature. Mostly the species are tall and straight. The whorled branching gives a typical conical or excurrent appearance to the plant (due to apical dominance). The plant body is sporophyte and the plants

are monoecious. The plant body is differentiated into roots, stem and leaves.

1. Root : A prominent tap root is present which does not penetrate deep into the soil. Lateral roots which develops later, grow extensively and help in anchoring the plant in the soil. Root hairs are scanty. Ectotrophic mycorrhiza i.e. symbiotic association of some fungal hyphae with the ultimate branches of roots, is of common occurrence.

2. Stem : The stem is erect, thick, cylindrical and branched. The branching is monopodial type. The main stem is covered by scaly bark. Branches are developed from the buds present in the axil of scale leaves and appear to be in whorls. These branches develop every year and help in calculating the age of the plant.

Branches are of two types :

Scale leaves

Foilage leaves (needles)

Dwarf shoot

lLong shoots  or  Branches  of  unlimited  growth  :

These have apical buds, grow indefinitely in whorls each

Long shoot

Scale leaves

year from the buds in the axil of scale leaves. These shoots spread out horizontally and bear scale leaves on them.

Fig : A part of Pinus stem showing two types of branches (long and dwarf) and two types of leaves(scale and foliage leaves)

• Dwarf shoots or Branches of limited growth : These branches lack apical buds and grow for a definite or short period. They arise in the axil of scale leaves on long shoots.

3. Leaves : The leaves are of two types i.e., dimorphic – scale leaves and foliage leaves.

• Scale leaves : The scale leaves are small membranous and brown. They are present on both types of branches (i.e. long and dwarf shoots). Scale leaves are non-photosynthetic. These protect the young buds.
• Foliage leaves : The foliage leaves are green, needle like and are born at the tips of the dwarf shoots only. Their size and number is different in different species. The dwarf shoot with needles is called a spur. On the basis of number of needles, spur is of different types as :

Monofoliar (with one needle), e.g., P. monophylla.

Bifoliar (with two needles), e.g., P. merkusi and P. sylvestris. Trifoliar (with three needles), e.g. P. gerardiana and P. roxburghii. Pentafoliar (with five needles), e.g., P. wallichiana, P. occelsa.

(ii)Internal structure

1. Root : The young root of Pinus is identical with the dicot root. A T.S. of root reveals the following structures.

• Epiblema : It is the outermost layer of compactly arranged cells. It gives out many thin and unicellular root hair.
• Cortex : It is c