768 PHYSIOLOGY. 



s'pore" This process is subject to various modifications in the 

 other genera in which it occurs. 



The second mode of fecundation of naked spores by ciliated 

 spermatozoids, occurs in the Melanosporese, and has been espe- 

 cially investigated by Thuret. His observations have been thus 

 condensed by Henfrey : — " In this order the conceptacles {fig. 

 840) produce in their interior, bodies of two kinds, antheridia 

 {figs. 840 and 842, a, a, a) and spore-sacs {fig. 840, sp), either 

 together or in separate conceptacles (monoecious), or in separate 

 plants. The antheridia discharge 2-eiliated spermctozoids {fig. 

 841), which are poured out through the pores of the receptacles 

 into the surrounding water. At the same time the spore-sac {fig. 

 840, 5p) bursts, and emits an inner sac, in which may be observed 

 2, 4, or 8 spherical corpuscles, destitute of a cellulose membrane ; 

 this inner sac, breaking loose, bursts and discharges its corpus- 

 cles, which, like the spermatozoids, pass through the pores of 

 the receptacle into the water. Here they become surrounded by 

 a cloud of spermatozoids, which attach themselves to the surface, 

 and by their ciliary movement cause the spores to revolve. In 

 the course of a few minutes, usualty, a cellulose membrane is 

 formed upon the surface of the globular corpuscle (by secretion 

 from its primordial utricle ?), and it becomes a cell, which subse- 

 quently germinates, growing by cell-division into a new frond." 



B. Reproduction of Acroge7ts. — Of the sexual nature of the 

 plants in all orders of this sub-division of the Cryptogamia 

 there can be no doubt. The sexual organs in all are also of an 

 analogous character, and are of two kinds, one of which is termed 

 an aoitheridium, which contains spirally wound ciliated sperma- 

 tozoids, and which is regarded as the male organ ; and the 

 other, called an archcgonium or pistillidium, in which an 

 embryonal cell or germ-cell is contained, which is the female 

 organ. Fecundation is supposed to be effected by the contact of 

 a sperm atozoid with an embryonal cell or germ-cell. In the 

 Characese no distinct archegonium occurs, but the nucule is con- 

 sidered as the representative of that structure. We have already 

 described the structure of the reproductive organs of Acrogens 

 (pp. 359 — 374), both before and after fertilization ; it will be only 

 necessary therefore, in the present place, to say a few words 

 upon the mode in which fertilization is supposed to take place 

 in the different natural orders included in this division of the 

 Cryptogamia. 



1. Characecb or Charas. — In this order we have two kinds of 

 reproductive organs, called, respectively, the ^/oiz(/g {fig. 816, g), 

 and the nucide {fig. 816, n) : the former is regarded as the r/ude ; 

 and the latter as the female. Fecundation is believed to take 

 place by the passage of the spiral spermatozoids of the globule 

 {fig. 817) down the canal which extends from the apex of the 

 nucule {figs. 819 and 820) to the central cell of the same struc- 



