286 On Azolla and Salvinia. 



lar appearance (it is altogether like nascent cellular tissue, 

 and its precursion by grume is like this too) to the same cause 

 as the apparent cellularity of the incrustation. In some 

 abortive trifacials may be seen. 



The changes that take place in the larger capsules from 

 the same period, chiefly affect the central sac, which, when 

 detached, will be found to present a similar, but relatively 

 smaller trifacial surface (PL 19. /. 5.) ; at this period this 

 sac is about equal in size to the trifacial cells, visible in 

 the circumference of the grume. But it never has presented 

 to me their empty appearance (PL 19. f. 2. S. 5.) 



The next period presented this central sac a good deal 

 enlarged, still apparently isolated ; it is surrounded by a 

 much thinner mass of grume, which from the frequent ab- 

 sence of the radiating* lines, often appears free of attach- 

 ments. The space between this grume and the inner wall of 

 the secondary capsule is more or less occupied by free trifacial 

 cells (PL 19. f. 3. 4. 8.) The grume itself on escaping from 

 the capsule will be found to present the trifacial cells, and 

 larger cells, (parent cells) exhibiting indications of division 

 {PL 19./. 6.) 



The central sac continues to increase : the grume sur- 

 rounding it to diminish, until it is reduced to a thin coating. 

 Generally about this period the sac has appeared to be at- 

 tached to the apex of the cavity of the secondary capsule 

 by means of grume ; occasionally traces of radiating lines 

 have been visible. The trilineal mark has mostly appeared 

 to correspond with the attaching mass of grume. 



The sac continuing to increase soon occupies the greater 

 part of the cavity of the secondary capsule ; it assumes a yel- 

 lowish colour; generally it appears to be freely pendu- 



* These lines are presumably unabsorbed or unaltered portions of the original 

 continuous grume. 



