394 PART IV. CLASSIFICATION. 



The female organ or archegonium is developed from a single superficial 

 cell at the centre of the upper surface of the prothallium (here several 

 cells thick) ; it does not call for any special description if the first arche- 

 gonium fails to become fertilised, others may be subsequently formed. 



The female cell or oosphere is contained in the venter of the archegonium. 



SUB-KINGDOM. 

 PHAXEBOGAMIA (OR SPEEMAPHYTA). 



The Gymnosperms and Angiosperms are all heterosporous plants, 

 having a definite alternation of generations, which is, however, 

 not readily perceived on account of the great reduction of the 

 sexual generation, and of the fact that the female gametophyte 

 remains enclosed in the macrospore, that the macrospore remains 

 enclosed in the macrosporangium, and that the macrosporangium 

 remains for a long time attached to the sporophyte, the result being 

 the development of a seed. The reduction of the gametophyte and 

 the formation of the seed are the features which essentially distin- 

 guish the Phanerogams from the higher heterosporous Pteridophyta 

 such as Selaginella and Isoetes. 



A. THE SPOROPHYTE. As in the Pteridophyta, so here, the plant 

 itself is the sporophyte or asexual generation. 



It is unnecessary to go into detail at present with regard to the 

 morphology of the vegetative organs, an account of which is given 

 in the section on General Morphology, and subsequently in the 

 description of the classes and orders. 



The Reproductive Organs of the sporophyte are sporangia of 

 two kinds, microsporangia and macrosporangia, which are usually 

 borne on sporophylls, but sometimes directly on the axis : the 

 modified shoots bearing the sporangia constitute flowers ; and 

 often bear, in addition to the sporophylls, other floral leaves (hyp- 

 sophylls, see p. 57), protective or attractive in function, some of 

 which usually constitute a perianth. 



The flowering shoot constitutes an inflorescence, which may 

 consist of one or many flowers, according to the extent to which 

 the shoot branches. 



The Flowsr see p. 55) is a sporangium-bearing shoot or sporo- 

 phore, of limited growth, with usually undeveloped or feebly de- 

 veloped internodes, so that the sporophylls and hypsophylls which 

 it bears are closely aggregated together. Most commonly the 

 flower includes both kinds of sporangia, that is, it is monoclinous 



