358 Dr. L. Radlkofer on Fecundation in the Vegetable Kingdom, 



prothallium above and soon displaying leaves ; the first adven- 

 titious root appears opposite to it. The end of the primary axis 

 expands in the internal cavity of the spore, displacing the cel- 

 lular tissue existing there. It is rare for more than one embryo 

 to be formed on a prothallium. 



B. IsoetecB. — The reproduction of Isoetes is the same in all 

 essential points as in Selaginella. The spermatozoids are deve- 

 loped in lenticular vesicles, which are produced singly or two 

 together in small cells formed from the contents of the micro- 

 spores (in their so-called germination). The spermatozoids are 

 filiform, with the anterior end thicker and ciliated, the posterior 

 attenuated ; the movement is slow compared with that in the 

 Ferns. Mettenius observed this first*. 



Hofmeisterf gives a complete history of the stages of develop- 

 ment of the embryo. It agrees in its essentials with that of Sela- 

 ginella, but the suspensor is wanting. Rarely more than one 

 embryo is developed on the same prothallium. HofmeisterJ 

 believes that he has often seen the remains of spermatozoids 

 which had ceased to move, lying in the archegonial canal. 



C. Lycopodiea. — There still exists here an essential gap in 

 our knowledge of the reproduction of the higher Cryptogamia. 

 The sowing of the spores of this group has never been attended 

 with any result hitherto, however frequent or varied the attempts 

 may have been. Since they only bear one kind of spore, it may 

 be conjectured that this produces in germination a prothallium 

 bearing both autheridia and archegonia. 



6. Phanerogamia. 



In the Phanerogamia Meyen§ attempted a comparison be- 

 tween the granules of the fo\-illa (in part starch-granules, as in the 

 Onagracese) which exhibit molecular motion, and spermatozoids, 

 calling these granules " spermatic molecules." Grisebach 1| 

 imagined that he found in the winter-buds of Rhamnus infectoria 

 and other plants an apparatus analogous to the anthcridia of the 

 Mosses and Ferns (to which at the same time he denied any 

 sexual import), believing that he found in them long-tailed cor- 

 puscles {"Phytozoa") either enclosed in a cell or swarming about 

 free. Itzigsohn did not hesitate to assert that these phytozoa 

 were the true spermatozoids of the Phanerogamia^. A produc- 

 tion of cellules in the pollen-tubes of the Coniferse, similar to 



* Beitr. z. Botanik, p. 16. 



t Beitr. z. Kenntn. der Gefassknptog. Abhandl. Sachsisch. Gesellsch. 

 der Wisseuschaft. iv. p. 123. Leipsic, 1852. See liere also for the other 

 bibliography on Isoetes. J Op. cit. p. 131. 



§ Pflanzenphysiologie, iii. p. 192. || Botau. Zeitung, 1844, p. 661. 



% Bot. Zeit. 1849, p. 560. 



