2 SPERM : ATOB-HYTA. 



all are flower-less and their methods of reproducing and propaga- 

 tion are varied. They contain no vascular tissue (except a few 

 large 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 

 undifferentiated 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 prothallium, an archegone of which is fertilized by means 

 of a tube (pollen-tube), a portion of the male prothallium sprout- 

 ing from the pollen-grain. 



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



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



Class 1. AXGIOSPERMAE. 



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



Class 2. GYMNOSPERMAE. 



Class 1. 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 to- 

 gether, in which the seeds are ripened. The pollen- grains (micro- 

 spores) on alighting upon the summit of the carpel (stigma) 

 germinate, sending 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. 



There are two sub-classes, distinguished as follows : 



Cotyledon one ; stem endogenous. Sub-class 1. MONOCOTYLEDONES. 



Cotyledons normally two; stem (with rare exceptions) exogenous. 



Sub-class 2. DICOTYLEDONS s. 



