382 Miscellaneous. 



spore. At the upper part of this some of the cells arc soon dif- 

 ferentiated and become " corpuscles," which wiU exactly represent 

 the archegonia. It is in their bosom that, when the j)roper moment 

 arrives, the germinal cells appear, and that fecundation is effected 

 by diffusion, the fecundating material successively traversing the 

 membrane of the pollen-tube and that of the corpuscles. 



It is here that the second period, or asexual generation, com- 

 mences ; and this, in the Phanerogamia, tends to acquire much 

 greater importance than the other. In proportion as the organs 

 which take part in the sexual generation are more degraded, those 

 which originate by asexual generation are more numerous and 

 perfect. 



We have not the time to follow here the whole development of 

 the embryo. We will only remark that it commences by li\-ing at 

 the expense of the endosperm, as the Cryptogamic embryo lives at 

 the expense of the prothaUium. The development of the second 

 generation is interrupted by a period of repose or lethargic sleep in 

 the heart of the seed — a fact which by no means weakens the theory. 

 When, the life of the young plant ha^•iug resumed its course, it has 

 arrived at its perfect form, it closes its biological cycle by the pro- 

 duction of organs of multiplication corresponding to the micro- and 

 macrospores — that is to say, the poUen- and embryonal sacs. As in 

 the Cryptogamia, these spores are produced by modified leaves ; the 

 fact is proved as regards the stamens, and is probable at least in the 

 case of the ovules. 



Lastly, thanks to the relations which unite them with the Gymno- 

 sperms, the phenomena of reproduction of the Angiospenus may be 

 reduced to the same general plan. The pollen-grain will still repre- 

 sent the microspore ; only there is no longer any trace of prothal- 

 lium, any more than of the mother cells of the antherozoids. The 

 development is limited to the expansion of the intine in the form of 

 a pollen-tube. 



In the embryonal sac, or macrospore, no archegonia are deve- 

 loped : the germinal cells originate directly in its midst ; but imme- 

 diately after fecundation it resumes its part, and becomes the seat 

 of the production of the endosperm or prothallium. The appearance 

 of this, here, follows instead of preceding fecundation. The two 

 periods are therefore less clearly limited in the Angiospenus than in 

 other plants. They nevertheless exist ; only the second, or asexual, 

 period tends always to predominate over the sexual period, as has 

 been indicated in the case of the Gymnosperms. 



Finally the embryo is developed ; and the asexual generation, as 

 in the preceding case, is divided by a period of repose in the heart 

 of the seed. At the end of the period of vegetation the plant always 

 closes its biological cycle by the production of organs of multipli- 

 cation ; only here the modifications are more profound, and, instead 

 of reaching only the leaf destined to produce the spores, they affect 

 the whole upper part of the axis, and thus is formed the flower with 

 its different whorls. 



Such is the series of arguments upon which the author founds his 



