178 UTRICULAR STRUCTURES, 



a circular constriction, which advances inwards, and at 

 last parts the chlorophyll-utricle into two. In other cases 

 a septum is first perceived, and the apparent constriction 

 is recognised to be simply a result of the retraction of the 

 already-formed secondary utricles from each other. Thus 

 a conviction is readily attained that in the first case the 

 septum is overlooked on account of its delicacy, or its 

 oblique position. 



It may, indeed, be objected that the said division is 

 merely apparent, and produced artificially by the close 

 apposition of two colour-utricles. Such a condition is 

 actually produced artificially, when two utricles come so 

 close together under the microscope, that they become 

 flattened by their mutual pressure. It is therefore a 

 question whether to take account of that apparent division 

 of the chlorophyll-utricle in the vegetable-cell, or not. 

 Nitella has furnished me with evidence for it. 



I examined the terminal cell of the leaves in various 

 stages of growth in the same individual, in Nitella syn- 

 carpa, namely, 1st, one measuring '080 of a line ; 2d, one 

 = '500; 3d, one =1*5; and 4th, one = 6 lines in length. 

 The diameters were from '030 to -050, '060, and '090 

 of a line. The chlorophyll-utricles lay in vertical rows 

 on the walls. They were all of about equal size, and ex- 

 hibited a perfectly regular shape, both in the young and 

 in the old cells. Some appeared to be in the commence- 

 ment of the act of division. Actual division and propa- 

 gation must take place if the number of chlorophyll- 

 utricles increase from the young to the old cells, since of 

 any very minute utricles which might originate free 

 among the others, I saw no trace, either between the 

 utricles of the same row, or between the rows. Now I 

 counted the rows, and found constantly about eighty of 

 them, both in the young and old cells. No multiplication 

 of the rows takes place ; in fact I did not see any chlo- 

 rophyll-utricle divide perpendicularly into two utricles lying 

 side by side. On the contrary, I found in the first and 

 shortest of the four cells mentioned, 40 utricles in a row ; 



