2 SPERMATOPHYTA. 



algae) and the plant body is not differentiated into stem and leaves. 

 Many of them are of microscopic size. 



Phylum 1. SPERMATOPHYTA. 



Seed-bearing Plants. 

 Plants producing seeds which contain an embryo formed of one or 

 more rudimentary leaves (cotyledons), a stem (hypocotyl, radicle), 

 and a terminal bud (plumule), or these parts sometimes undifferen- 

 tiated before germination. Microspores (pollen-grains) are borne 

 in microsporanges (anther-sacs) on the apex or side of a modified 

 leaf (filament). The macrosporanges (ovules) are borne on the face 

 of a flat or inrolled much modified leaf (carpel) and contain one 

 macrospore (embryo-sac) ; this develops the minute female prothal- 

 lium, an archegone of which is fertilized by means of a tube (pollen- 

 tube), a portion of the male prothallium sprouting from the pollen- 

 grain. 



There are two classes whicli differ from each other as follows: 



Ovules and seeds contained In a closed cavity (ovary) ; stigmas 1 or more. 



Class 1. Angiospekmae. 

 Ovules and seeds borne on the face of a scale ; stigmas none. Class 2. Gymnospermae. 



Class I. ANGIOSPERMAE. 



Ovules (macrosporanges) enclosed in a cavity (the ovary) 

 formed by the infolding and uniting of the margins of a modified 

 rudimentary leaf (carpel), or of several such leaves joined together, 

 in which the seeds are ripened. The pollen-grains (microspores) on 

 alighting upon the summit of the carpel (stigma) germinate, send- 

 ing out a pollen-tube which penetrates its tissues and reaching an 

 ovule enters the orifice of the latter (micropyle), and its tip coming 

 in contact with a germ-cell in the embryo-sac, fertilization is effected. 

 In a few cases the pollen-tube enters the ovule at the chalaza, not at 

 the micropyle. 



Cotyledon mostly one ; stem endogenous. Sub-class 1. Monocotyledones. 



Cotyledons mostly two; stem (with rare excep- 

 tions) exogenous. Sub-class 2. Dicotyledokes. 



Sub-class 1. MONOCOTYLEDONES. 



Embryo with a single cotyledon and the first leaves of the 

 germinating plantlet alternate. Stem composed of a ground-mass 

 of soft tissue (parenchyma) in which bundles of wood-cells are 

 irregularly imbedded; no distinction into wood, pith and bark. 

 Leaves usually parallel-veined, mostly alternate and entire, com- 

 monly sheathing the stem at the base and often with no distinction 

 of blade and petiole. Flowers often 3-merous or 6-merous. 



