502 MARSILEACEiE. 



The next step consists in both tunics becoming tawny : 

 they are still all of the same size, and the appearances of 

 division are not increased. 



At a later period they become surrounded by a mucilagin- 

 ous envelope, which is at first faint, and they are unequal in 

 size. At this period, they fill entirely the cavity of the capsule. 

 At a subsequent period they are still more unequal in size, 

 of the same colour, and surrounded with a distinct mucila- 

 ginous envelope. 



They undergo no father change, beyond maturation. 



The additional or mucilaginous envelope obviously origin- 

 ates in the grumous mass in which the sporules are form- 

 ed, its different stages of developement and separation, being 

 distinct enough. 



The inequality of the sporule is attributable to the very 

 different periods at which the portions marked out by the 

 dividing lines become separate. This process appears to 

 commence in the sporula of the circumference ; when it takes 

 place, each mass carries with it a tunic from the mucilagin- 

 ous coat. So soon as it has been perfected, the convexo- 

 concave sporule adopts a tendency to become globular, and 

 at the same time granules, or very small cellules are developed 

 in its interior. Tne innermost compound sporula at a late 

 period preserve the same appearance that they had on first 

 becoming coloured, with the exception of the addition of the 

 mucilaginous envelope. 



The fact of the different periods of separation, accounts 

 satisfactorily for the various appearances presented by the spo- 

 rula at a late period of developement. We have on the circum- 

 ference rather large and perfect sporula, in the centre smalt 

 transparent compound sporula, and between these every gra- 

 dation of size, but all more or less convexo-concave, those to- 

 wards the centre being the most so ; contiguous to the inner 

 most unseparated compound sporula, we have some undergo- 

 ing separation, but still enclosed in a common mucilaginous 

 tunic. 



