82 BOTANY AND PHARMACOGNOSY. 



of the plant kingdom. They vary in size from diminutive plants 

 Hke the windflower to the giant oak which shelters it. They may 

 accomplish their life work in a few months, as the common stra- 

 monium, or they may persist for several hundred years, as the 

 trees of our primitive forests. They may inhabit dry desert 

 regions, as the Cacti and Chenopodiaceae, or they may live wholly 

 in water, as the water lilies. In short they show the greatest 

 adaptability to their surroundings. But no matter how diversified 

 they may seem in form and structure, they agree in this with 

 possibly one exception, namely, mignonette, that the seeds are 

 produced in a closed carpel. This has been considered, as already 

 indicated, to be the chief difference between the Gymnosperms 

 and Angiosperms. 



The two groups are further distinguished by several other 

 important characters: (i) the carpel or carpels (megasporophyll) 

 is developed into an organ commonly known as a pistil (Figs. 



83 and 85). This organ consists of three parts, namely, ovary, 

 style and stigma, the ovary enclosing the ovules (Figs. 83, 85). 

 In the Angiosperms the megaspore (embryo-sac) develops a 

 gametophyte which does not give rise to archegonia, but the egg 

 arises directly from the megaspore nucleus by a series of divisions. 



(3) The Microsporophyll (stamen) dififers considerably in 

 structure and appearance from that of the Gymnosperms. The 

 stamen may be defined as a leaf which bears sporangia (spore 

 cases). It usually consists of the following differentiated parts: 

 filament and anther, the latter consisting of pollen sacs (micro- 

 sporangia) in which the pollen grains (microspores) are devel- 

 oped (Figs. 81, 83 and 85). (4) In a large number of cases in 

 the Angiosperms there is developed in addition to the sporophylls 

 or sporangial leaves (stamens and pistils) another series of 

 leaves known as floral leaves (Fig. 83). The latter usually are 

 of two kinds, known as sepals and petals. 



The Development of the Two Generations, namely, the 

 sporophyte and gametophyte, is much the same in the Angio- 

 sperms as in the Gymnosperms. That is, the sporophyte consti- 

 tutes the plant body and what is commonly considered to be the 

 plant. The gametophytes are still more reduced than was the 

 case in the Gymnosperms, the male gameto])hytc consisting of 

 but two cells. 



