462 PART III. — 'THE CLASSIFICATION OF PLANTS. 



complete the whole course of their development in a single year, 

 as the Wheat ; and biennials, which do not blossom until the 

 second year of their life, when they perish, as the Turnip, Carrot, 

 Beetroot, etc. By polycarpous plants are meant such as produce 

 flowers and fruit year after year; such are trees and shrubs, as 

 also many herbaceous plants which have underground rhizomes, 

 tubers, etc. 



The group of the Phanerogams falls into two natural divisions ; 

 the one containing but a single class; the other, two classes. 



A. GYMNOSPERM^. 



Sporophy tic Characters. The ovule is not enclosed in an ovary, 

 nor is there any style or stigma : in pollination, the pollen-grain 

 enters the micropyle and comes into direct contact with the 

 nucellus : the flowers are never ambisporangiate, and are generally 

 without a perianth : there are no companion-cells in the phloem, 

 and the secondary wood does not (except Gnetacese) contain true 

 vessels. 



Gametophytic Characters. The female prothallium is completely 

 formed before fertilisation: the female organ is generally a well- 

 developed archegonium. 



Class I. — Gymnosperm^. 



B. ANGIOSPERM^. 



Sporophytic Characters . The ovule is enclosed in an ovary, and 

 there is always a stigma : the pollen-grain does not come into 

 direct relation with the ovule, but falls upon the stigma and 

 germinates there : the flowers are commonly ambisporangiate and 

 possess a perianth : there are companion-cells in the phloem, 

 and the secondary wood generally includes true vessels. 



Gametophytic Characters. The female prothallium is only partly 

 formed before fertilisation : the female organ is a reduced uni- 

 cellular archegonium. 



Class I. — MoNOCOTYLEDONES. The embryo has but one cotyle- 

 don : the ripe seed is usually albuminous. 



Class II. — DicoTYLEDONES. The embryo has two opposite coty- 

 ledons : the ripe seed is frequently exalbuminous. 



