GROUP IV. PHANEROGAM1A. 



431 



GROUP IV. 

 PHANEROGAMIA (OB SPERMAPHYTA). 



THESE 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 

 which constitutes a characteristic feature of the group (see p. 217). 



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 ; full information is 

 given in the section on General 

 Morphology, and subsequent- 

 ly 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 sporo- 

 phylls, but sometimes directly 

 on the axis : the modified 

 shoots bearing the sporangia 

 constitute flowers ; and they 

 usually bear, in addition to 

 the sporophylls, other floral 

 leaves (hypsophylls, see p. 

 79), protective or attractive 

 in function, some of which 

 usually constitute a perianth. em the embryo-sac. E The oosphere. 



The flowering shoot consti- 

 tutes an inflorescence, which may consist of one or many flowers, 

 according to the extent to which the shoot branches. 



The Flower (see p. 76) is a sporangium-bearing shoot or sporo- 

 phore with usually undeveloped or feebly developed internodes, 



FIG. 290. Diagram of an angiospermous 

 flower. Ke Calyx. K Corolla j / filament of 

 stamen ; a anther with two pollen-sacs in each 

 half which are opened, showing the pollen- 

 grains (p). These fall on the stigma, and the 

 pollen-tube (ps) penetrates the style (g) as 

 far as the cavity of the ovary (F), reaching 

 the ovule (S) ; i the integument of the ovule; 



V. S. B. 



F F 



