AZOLL A AND SALVINIA. 



527 



grumous condensation in the original nucleus ; (PI. CXX. Fi g 

 III., PI. CXXI. Fig. III.) of the latter, the development of 

 grumous matter in each of the small protuberances round the 

 base of the nucleus, which are developed in a centrifugal order 



In the first which I now propose to follow, this condensa- 

 tion, for so it apparently is, increases until a tolerably well 

 defined opaque grumous disc is seen in the nucleus : this disc 

 subsequently appears under a certain focus transparent in the 

 centre, opaque round the edges (PI. CXXII. Fig. IV. 15 ; PI. 

 CXXI. Fig. V.) ; an appearance due, I believe, to the develop- 

 ment of a membranous sac inside. In the meantime, the pink 

 colour of the cells of the surface of the organ has increased, 

 so has the browning of the apex, which still often presents 

 traces of adhering moniliform filaments. Both organs also ex- 

 habit distinct vessels prolonged from the vessels of the axis 

 into their bases. (PI. CXX. Fig. III., PI. CXXI. Fig. III.) 



The next stage presents nothing particular in the appear- 

 ance of the organ or the enclosed monilifom filaments. The 

 nucleus however, presents about its centre, in lieu of the 

 grumous disc transparent in the centre, a well defined small 

 yellow sac, and between it and the apex of the nucleus, 

 a grumous mass is seen presenting what appear to be several 

 small points of condensation. (PI. CXXI. Fig. I.j Somewhat 

 later the organ having increased a little in size, the yellow 

 sac is found to be as it were capped by the grumous mass, 

 (PL CXXI. Fig. VII. PL XX. Fig. V.c,) which presents 

 shortly after indications of division (lobes) on its surface. 

 PI. CXIX. Fig. I., 2, 3. 



The space between the apex of the nucleus, and the now 

 very brown apex of the organ, still presents the dislocated 

 joints, which now form a column of communication between 

 the foramen and the nucleus (PL CXXI. Fig. VI.) ; parts of 

 the moniliform filaments may often also be found adhering to 

 the foramen itself. 



The lobes mentioned as appearing in the capping grume 

 continuing to be developed, encroach upwards on the nucleus 

 (PL CXIX. Fig. I aj 3.) ; and the yellow sac, which, as the 



