45« 



VASCULAR CRYPTOGAMS. 



antherozoids penetrate after germination (comp. Fig. 314)- The macrospores of 

 Marsilia possess a similar epispore, the development of which has been very fully but 

 not very intelligibly described and figured by Russow. According to him the muci- 

 laginous investment of the abortive sister-cells passes over to the macrospore and 

 forms the first layer of its epispore ; then a protoplasmic vesicle encloses the whole 

 macrospore, and within this the thick prismatic layers of the epispore are developed. 

 Russow's account confirms the view which I had already expressed that these 

 investing layers are deposited from without, a view which is rendered even more 

 probable by the facts kndwn concerning these processes in the Salviniaceae, but 

 it makes the whole process somewhat obscure, and I have no material at present for 

 a fresh study of the formation of the epispore in the Marsiliaceae. 



The ejection of the macro- and microspores from the very firm sporocarps is 

 associated with some remarkable processes, for a knowledge of which we are 

 indebted to Hanstein. The ripe fruits of Pilularia glohulifera lie either in moist 



Fig. 324.— Further development of the macrospore c^i Pilularia glolmlif era; h cavity of the spore, a the first inner coat, /' the 

 second, c the third, d the fourth coat ; the second, third, and fourth together form the epispore {X 80). 



earth or upon it ; the wall splits at the apex into four valves, and a hyaline 

 viscid mucilage, evidently derived from the tissue separating the chambers, escapes 

 and forms a drop upon the surface of the soil which continues to increase in size for 

 some days. In this mucilage the microspores and the macrospores are carried out, 

 and they germinate in it. When fertilisation has taken place the drop of mucilage 

 becomes fluid, and leaves the fertilised macrospores on the moist ground to which 

 they are attached by the root-hairs of their prothallia until the first root of the 

 embryo penetrates it. Fig. 325 represents the most important of the corresponding 

 processes in the case of Marsilia Salvairix. If the sporocarp, which is as hard as 

 a stone, be slightly injured along its ventral margin and be then placed in water, the 

 water gains access to the interior and causes the tissue forming the walls of the 

 chambers to swell-up, and the result is that the testa splits along its ventral side into 

 two valves. It is shown in Fig. 325, B^ that a hyaline ring protrudes, which lay pre- 

 viously in the angle along the ventral edge, and carries with it the chambers 



