I30 PLANT LIFE. 



preceding orders, but distinguished by its complexity, and by 

 the fact that the fertilized oosphere— the oospore — never 

 germinates directly, but undergoes further cell-division pre- 

 vious to the formation of bodies capable of germination 

 known as carposfiores. Thick-walled resting-spores, the 

 immediate result of fertilization, are unknown in the present 

 order. 



In the simplest type, illustrated by the genus Batracho- 

 spennum, the carpogonium consists of a single cell, continued 

 at the apex into a long, thin trichogyne. After fertilization 

 the carpogonium divides into two cells, the uppermost one 

 along with the trichogyne disappears, the lower one contains 

 the fertilized oosphere, and soon becomes divided into 

 several cells : these cells bulge outwards and form a dense 

 cluster of short branches, the terminal cells producing the 

 carpospores. The entire structure is enclosed in a gelatinous 

 pellicle. 



In the more complex condition the carpogonium consists 

 of one or more fertile cells, in addition to one or more sterile 

 cells forming the trichophore, terminated by the trichogyne, 

 which in the present order always remains closed at the 

 apex. In the genus Crouania and some others, each cysto- 

 carp has usually two trichogynes. After fertilization the 

 carpogonium becomes differentiated into a central portion, 

 the placenta, from which spring the carpospores, often pro- 

 duced in simple or branched chains. In the genus Calli- 

 thamnion, the carpospores are only enclosed in a gelatinous 

 covering, whereas in Polysiphonia and the majority of 

 genera the carpogonium becomes surrounded by a pericarp 

 consisting of closely-apposed branchlets : the entire structure 

 is then known as a cystocarp. In the genus Gracilaria the 

 pericarp is developed before fertilization. 



