116 



DOMESTIC BOTANY. 



With regard to the fertilization of Ferns and Cryptogams in 

 general little can here be said. The microscope has revealed 

 the presence of organs that apparently perform the same 

 functions that stamens and pistils do in Phsenogams, 



The Fern spore vegetates in the form of a simple, oblong 

 cell, from which other cells are successively produced, ulti- 

 mately forming a thin green membrane, called the prothallium, 

 which lies nearly flat, and attaches itself by the aid of fine 

 spongioles to the surface. When of full size it is round or 

 oblong, varying from a quarter to half an inch in diameter, 

 and having the appearance of a small foliaceous lichen. In 

 the progress of its growth peculiar cells are formed on its 

 under surface of two kinds — one called Antheridia, the other 

 Arcliegonia ; the first containing round cells called sperm 

 cells, which contain minute worm-like bodies, that issue from 

 the cells when arrived at maturity. The cells of the Arche- 

 gonia differ considerably in their structure from the Anthe- 

 ridia ; they contain an embryonal sac, which at a certain 

 period protriides from the cell, and with which the moving 

 spermatozoids are said to come in contact, and thus produce 

 fertilization. Soon after this the embryo sac is changed, a 

 bud is formed, and ultimately a young fern plant is gradually 

 developed ; in time the prothallium dies. 



