64 



MOSSES AND FERNS 



CHAP. 



growth, and through the foot nourishment is conveyed from 

 the thallus to the developing capsule. That is, the sporogo- 

 nium is here a strictly parasitic organism, growing entirely at 

 the expense of the thallus. 



The further growth of the spores and elaters was studied in 

 Finihriaria Calif ornica. The spores remain together in tetrads, 

 until nearlv ripe. In sections parallel to the surface of the 

 younger spores (Fig. 26, C) the outer surface of the exospore 

 is covered with very irregular sinuous thickenings, at first 

 projecting but little above the surface, but afterward becoming 

 in this species extraordinarily developed. In sections of the 





Fig. 26. — Fimbriaria Californica. A, Young elater X6oo; B, a fully-grown clater, 

 X300; C, surface view of the wall of a young spore, showing the developing 

 episporic ridges, X6oo; D, section of a wall of a ripe spore, X300. 



ripe spore (Fig. 26, D) three distinct layers are evident, the 

 cellulose endospore, the thick exospore, and this outer thick- 

 ened mass of projecting ridges which has every appearance of 

 being deposited from without, and must therefore be charac- 

 terised as epispore (perinium) ; Leitgeb ((7), vi., p. 45) dis- 

 tinctly states that thickenings of this character do not occur in 

 the MarchantiecT, but that the thickenings are always of the 

 character of those in Riccia. 



