M. H. V. Mohl on the Structure of Chlorophyll. 419 



in most cases, that the globules are imbedded in a mucilaginous, 

 transparent mass, by which they are attached to the internal 

 surface of the primordial utricle, or with which, in particular 

 cases, as in Vallisneria^, they are carried along in a flowing 

 movement. In most cases no definite relation can be detected 

 between these parietal chlorojjhyil-globules and the nucleus and 

 the currents of protoi)lasm issuing from it ; in other instances, 

 on the contrary, the connexion is very manifest. For example, in 

 the parenchyma-cells of the stem of the Setaginell(c, the chlo- 

 roj)hy 11 -grains lie in moniliform rows in the protoplasm-threads, 

 which creep out over the cell-wall from the parietal nucleus ; and 

 in the Potato, if allowed to become green in the light, chlo- 

 rophyll-grains are formed in the accumulation of protoplasm 

 surrounding the nucleus, and in the threads radiating from this, 

 in the cells devoid of starch-grains which lie beneath the corky 

 layer. 



In regard to the structure of the chlorophyll-globules, inves- 

 tigation of a large number of plants enables us to distinguish 

 two varieties, which in their extreme forms exhibit important 

 differences, not however sharply defined, but passing into one 

 another by a multitude of intermediate stages. 



One form consists of globular, but ordinarily flattened grains, 

 with one of their flat sides attached to the cell-wall, the dia- 

 meter not often exceeding -^^q to ^j-^ of a line, frequently not 

 attaining this magnitude. When crowded together, their cir- 

 cumference assumes, like that of epidermal cells, a six-sided, but 

 not acute-angled form ; as this form is undoubtedly the result 

 of mutual pressure, this existing notwithstanding that the 

 grains are not in immediate contact, it may be fairly concluded, 

 that they are imbedded in a mucilaginous layer not always recog- 

 nizable by the microscope, the mutual pressure being communi- 

 cated through this mucilage. We may distinguish in their sub- 

 stance, frequently how^ever not until after the action of water, 

 fine globules attaining a diameter of about 2 o'oo °^ ^ \\'^Q, which 

 sometimes ])roject upon the surface of the grain, so that its cir- 

 cumference is not bounded by a uniformly curved line, but 

 appears irregularly toothed. 



Water very quickly exerts a considerable influence upon these 

 globules. As soon as it penetrates through an opening into the 



* I may take this opportunity of adiling, that in the cells which form 

 the partitions of the air-cavities in the leaves of CeratophyUiim demersum, 

 the chlorophyll-granules exhibit a motion like that in VaUisncria, but so 

 slow, that in two cases in which I measured it carefully, they only advanced 



' ■ and — — of a line in a second. FThis circulation mav be well seen m 



21,660 24,000 ^ 



the same manner in the cells of the leaves of Anacharis Alsinastrum, but 

 it appears to vary much in rapidity according to circumstances. — A. H.j 



