oe. 
Special Mi orphology and : Classification. 318 
leaf-like often kidney-shaped structure, lying flat on the 
surface of the ground, the srothallium or pro-embryo (Fig. 
AAI I11.), which puts out root-hairs |7hzzozds| from its under 
side, and forms the archegonia and antheridia among them. 
In the former are produced the ciliated antherozoids (Fig. 
442); from the latter, which agree in almost all points with 
Fic. 442.—Antheridia of Adiantum capillus-veneris, maidenhair-fern; I. not yet | 
mature; IJ. the antherozoids fully developed; III. the antherozoids escaping 
from the burst antheridium ; # prothallium, @ antheridium, s antherozoids, 6 
mother-cell of an antherozoid (x pee) 
the archegonia of Mosses, the young plant is developed, 
after the fertilisation of the oosphere by the mean 
the prothallium then disappearing.! 
An alternation of generations is very strongly marked in 
Ferns ; the first [sexual] generation includes the formation of 
the prothallium and sexual organs ; the second [non-sexual | 
1 [The central cell. of the archegonium divides first into four cells, 
of which the two lowest subdivide and become imbedded ih the sub- 
stance of the prothallium. The two upper of the four cells also sub- 
divide, one developing into the rhizome, the other into the first rootlet . 
of the young Fern.—ED. ] | 
