ACROGENS. 281 
for a few weeks, and which still consist of only a small number 
of cells. For this most important discovery we are indebted, 
in the first place, to Herr Negeli, and it was confirmed some 
year later by the observations of Herr Leszcyce-Suminski. eee 
If we follow the germination of a fern-spore with Herr Suminski, 
we find that its external membrane, resistant and coloured, is 
broken, and by the opening thus formed in the external membrane 
issues, in the form of a sort 
of tube, certain cellules re- 
producing and multiplying 
themselves at the extremity 
of the tube. From this 
there results sometimes a 
small foliaceous expansion, 
heart-shaped, in the form 
of a pear (Fig. 344, a), 
whose dimensions in Pteris 
serulata may be an eighth « @* 
of an inch bya tenth. In —_ 
the upper part of this small 
organ or prothallium would 
appear in due course the 
root or radicle, then the 
antherid, and finally the ar- 
chegonium would appear. 
The antherids are small i] 
cellular mamelons, formed, 
according to M. Thuret, of 
ring-like cellule, is only filled with a greyish granulose 
matter; by degrees, small sperical bodies are seen, which are 
the antherozoids, As these develop themselves the central cavity 
Mereases in volume, and presses strongly upon the walls of the | 
Peripheric cellule. Finally the time comes when the prosvaxe a 
-*° Great that the antherid is suddenly burst; the uppermost ee 
