M. Miiller on the Development of the Lycopodiaccse. 245 



occupies the whole of the interior : this also consists of delicate 

 parenchymatous cells, which are veiy densely filled with a forma- 

 tive matter (reddish cytoblastema) : they are the mother-cells 

 of the spores. By the examination of the interior we now un- 

 derstand, why the layer of mother-cells of the spores is often 

 compressed in an evident degree, and why, when seen through 

 the young and delicate membrane of the antheridium, they ap- 

 pear globular. The greater or less degree of compression depends 

 of course on the thickness of the epidermis and the subjacent 

 cellular layer. 



Passing to Psilotum, we find, in a delicate longitudinal section 

 of the sporangium, the same layer of mother-cells which we meet 

 with in L. denticulatum (PL V. fig. 12). However, the layer of 

 empty cells which follow close upon the epidermis of L. denticu- 

 latum does not exist here. The mother-cells, tolerably regular in 

 form and of large size, lie closely upon the very thick epidermis 

 of the sporangium of Psilotum ; they are also distended by a 

 reddish mass, which, agglomerated into a spherical form, may 

 clearly enough be perceived to consist of cytoblasts. If the cy- 

 toblast has been cut through a little out of the centre, the central 

 nucleus also is perceived in its granular, distinctly evident sub- 

 stance. These mother-cells are therefore formed through cyto- 

 blasts in the first instance, and fill the interior of the sporangium 

 as a large-celled parenchymatous tissue. 



The sporangium now swells, and this process depends on the 

 expanding mother-cells (fig. 13). This swelling out and exten- 

 sion act in such a manner that the membranes of the mother- 

 cells acquire an extraordinary degree of transparency, which may 

 be so increased in later stages, that unless one has very sharp eyes 

 and observes with great attention, the cell- walls will be certainly 

 overlooked. I shall return once more to this. The expansion 

 of the mother-cells is combined simultaneously with that of the 

 cytoblasts contained in their interior : this is in consequence of 

 their outer borders becoming dissolved or rather macerated in 

 water, since the softened mass is almost always granular. The 

 latter thus becomes mucilaginous. The cytoblast becomes gra- 

 dually smaller, but is usually so equably dissolved that it always 

 appears globular (fig. 13). Sometimes however it is oval (fig. 14) : 

 this only occurs if the mother-cells no longer lie, as in the 

 former case (fig. 13), one upon another as tumefied cellular tis- 

 sue, but when the individual cells have become perfectly sepa- 

 rated from each other, and thus lie so much freer in the interior 

 of the sporangium. That the sporangium undergoes proportional 

 expansion with the actual enlargement of the mother-cells is to 

 be understood in all cases. 



The expansion of the mother-cells proceeds with continually 



