S38 



EEPKODUCTION IN 



■which the inner is the true cell-wall, and the outer a sort of secre- 

 tion from it. In germination, the inner or proper membrane of the 

 spore swells, and protrudes, from any part of its surface favorably 

 situated, a tubular process, which forms partitions as it elongates 

 and branches, giving rise to what has been fancifully named a pro- 

 embryo, or, better, a prothcdlus, — a rudimentary plantlet very unlike 

 a Moss, but closely resembling a branched Conferva, consisting, as 

 it does, merely of ramified threads, or rows of cells. After a time 

 .certain cells of its various branches, faking a special development, 

 produce buds, which are soon covered with a tuft of rudimentary 

 leaves, and grow up intp the leafy stems of the perfected plant. Here 

 a single spore — or rather a peculiar transitory plantlet developed 

 from it — gives rise at once to a number of individuals. And in 

 fecundation it is not the spores themselves that are fertilized, but 

 a cell which by its development gives origin to a spore-case, and this 

 to a vast number of spores.* 



6G3. Fertilization of a Cell of a Prothallus, or peeuliar germinating 

 Plantlet, which thereupon develops into a Plant. This most extraordi- 

 nary mode of fecundation has recently been discovered in the Ferns 

 and other of the higher Cryptogamous orders. The fructification of 

 Ferns consists of spore-cases alone, which are borne on the back, 

 margins, or some other part of their leaves (Fig. 1287-1294), and 

 are filled with spores resembling those of Mosses. Since Mosses have 

 long been known to have organs answering in function to stamens, 

 as well as those answering to pistils, and since Ferns are regarded 

 as plants of higher rank than Mosses, their antheridia were diligent- 

 ly sought for upon the fructifying plants, but in vain ; and botanists 

 were therefore forced to the unwilling conclusion, that the highest 

 organized of Cryptogamous plants were asexual. But antheridia, 

 essentially like those of Mosses, have been at length detected, not upon 

 the mature and fructifying plant, but upon the germinating plantlet. 

 The germination of the spores of Ferns had long since been ob- 

 served. The process begins in the same manner as in Mosses ; but 

 the extremity of the tubular prolongation of the spore, converted 

 by partitions into a row of cells, is developed into an expanded, leaf- 

 like body (the pro-embryo, or prothallus as it is now called), which 



* The fullest account is by Hofmeister, Vergleichende Unlersuchurujen der 

 Keimunff, Entfaltung, und FruchtUldung Hoherer Kryptogamen, etc. — Leipsic, 

 1851. 



