sticky part, the stigma. Inside the ovule 

 chamber are one or more ovules (macro- 

 sporangia), in which the macrospores are 

 formed. 



The flowers of different species exhibit 

 many variations (Figs. 12-16 to 18). Usually 

 both stamens and pistils are present, but 

 some plants possess two kinds of incomplete 

 flowers, one containing only stamens (stami- 

 nate flowers), and the other containing only 

 pistils (pistillate flowers). These kinds of 

 flowers may be borne on the same, or upon 

 separate individual plants. Plants bearing 

 only staminate flowers may be referred to as 

 male, and those with only pistillate flowers 

 as female plants; but in either case, the sporo- 

 phyte plant does not give rise directly to the 

 sperm or eggs. 



Essential Nature of the Floral Parts. The 

 essential nature of the floral structures is 

 difficult to comprehend, except in compari- 

 son with equivalent structures in the non- 

 flowering plants. The ovules- that develop 

 in the ovule chamber are equivalent to the 



2 Strictly speaking, only the inner part (nucellus) of 

 the ovule is equivalent to the macrosporangium. 



Reproduction in Multicellular Planis - 219 



sporangia of other plants, or more specifi- 

 cally, to the macrosporangium of Selaginella. 

 In seed plants, however, only one macrospore 

 is formed in each ovule (macrosporangium). 

 This single large haploid cell is formed by 

 meiosis from a macrospore mother cell 

 (macrosporocyte), and lies near the center of 

 the ovule (Fig. 12-14). During the two divi- 

 sions of meiosis most of the cytoplasm is re- 

 tained by one of the four daughter cells, and 

 this cell becomes the functional macrospore. 

 The macrospore lies in direct contact with 

 three smaller sister "spores" (Fig. 12-19), but 

 the three smaller cells are sterile. Eventually 

 they disintegrate and do not play any further 

 part in reproduction. 



The Gametophytes of the Angiosperm. 

 Like the spores of other plants, the macro- 

 spore is a haploid cell that is destined to 

 develop into a gametophyte — in this case the 

 female gametophyte of the species. But the 

 female gametophyte of the seed plant never 

 attains anything but a microscopic size. At 

 maturity it consists of only eight cells, includ- 

 ing the egg cell and the two endosperm 

 nuclei (Fig. 12-19). The diminutive female 



Fig. 12-18. The flower of the peony is considered to be primitive, since it has 

 numerous stamens and several separate, simple pistils (in the center of each 

 flower). (From College Botany, by Fuller and Tippo. Holt, Rinehart and Winston, 

 Inc.) 



