20 



and the resemblance to Chara, so happily conjectured, are so com- 

 pletely borne out by what I have observed in Nitella, that the descrip- 

 tion of the one might almost serve for that of the other. 



In some specimens of Nitella Jlexilis (PL ii. fig. 6) the circulation 

 was observed to be going on vigorously up to the 4th of April, 1 835 : 

 on the 6th, two days after the last observation, the circulation "had en- 

 tirely ceased. The green particles lining the interior of the stems 

 and branches had shrunk from the parieties, and, together with the 

 green circulatory matter of the interior, was collected together in ir- 

 regular masses within the tubes, (PI. ii. fig. 7) ; but none of the brown 

 bodies afterwards observed were as yet apparent in any of the pieces. 

 t On the 11 tli, five days after the preceding observation, and no in- 

 termediate one having been made, the same specimens were again 

 examined, and were found to present characters which I had not be- 

 fore observed. In many of the joints, the irregular masses of green 

 matter had resolved themselves into globular bodies of variable size 

 but definite form, and had changed from a green to a rich brown color. 

 About half of the joints had undergone this change, the other half re- 

 maining in the green state, as at the last observation, but the circula- 

 tion had entirely ceased in all, and the plant was evidently dead. 



In the greater number of those joints which contained the brown 

 bodies, the green matter had entirely disappeared, leaving the tubes 

 as transparent as glass, with the brown globules like rows of beads ir- 

 regularly scattered in their interior, (PI. ii. fig. 8 a, and fig. 9). These 

 varied very considerably in number. In one long joint of the plant 

 about eighty of them were counted, while in one of the short branches 

 there were only five. Some of the larger bodies were about half the 

 diameter of the tubes in which they were contained, while others were 

 one eighth of the diameter. Those which were completely formed 

 had all the same character. They consisted of tolerably regular 

 spheres, except where their form had been slightly altered by lying 

 in contact with each other. In almost all of them, however, and es- 

 pecially in the larger ones, there was a slight flattening or a cup-like 

 depression at one point, which was generally observed to be directed 

 towards the surface of the tube, and might have been produced by the 

 globules coming in contact with the parietes of the tube, but was ne- 

 vertheless retained after they were extracted from it. In the centre of 

 the flattened portion or cup-like depression, there was always observed 

 to be a small collection of granules, which were of the usual size of 

 the globules of circulation, but also of a brown colour, (PI. ii. fig. 10 

 a). The brown bodies, on account of the now transparency of the 



