M. H. V. Mohl on the Structure of Chlorophyll. 337 



essentially different chemical composition. In reference to this 

 we should note particularly that Mulder, who certainly has claim 

 to give an opinion here, could demonstrate proteine in it in many 

 cases, but not in all, and states that he does not know the com- 

 pound of which it is composed (Physiological Chemistry, Edin- 

 burgh, Translation, p. 409). With this slight knowledge pos- 

 sessed of the chemical characters of the primordial utricle, 

 Nageli's theory that it owes its origin to a coagulation of a pro- 

 teine-substance, caused by the cell- sap, is unfurnished with any 

 safe foundation. 



With Nageli must be named particularly, among the cham- 

 pions of the utricular nature of the chlorophyll -granules, Gop- 

 pert and Cohn, who in their essay on Nitella (Botanische Zeit- 

 ung, 1849, p. 681), published in the interval between the two 

 works of Nageli above mentioned, gave a minute account of the 

 chlorophyll-granules of this genus. They came to the con- 

 clusion, that although the chlorophyll-granule in general did 

 not allow of the demonstration of any definite structure during 

 life, yet the alterations which it underwent in water prove that 

 it is composed of a clear, colourless membrane which becomes 

 distended in water, of green fluid contents, and several solid 

 nuclei composed of starch. 



Passing to the exposition of results of my own investigations, 

 it will be most to the purpose to examine first the character of 

 the chlorophyll of Zygnema^ since the great mass in which the 

 chlorophyll occurs here, in the form of the well-known spiral 

 bands, greatly facilitates the investigation, if we select for exa- 

 mination the larger species, such as Z, nitidum. I have shown 

 in my former essay, that these green bands agree, in the most 

 essential conditions of their structure, with chlorophyll-granules, 

 since, like the latter, they are composed of a soft substance, 

 coloured brown by iodine, which owes its green colour to an ex- 

 tremely small quantity of colouring matter, so that the share 

 which the latter takes in the formation of the entire mass cannot 

 be determined. The roundish granules which occur at intervals 

 in the median line of the chlorophyll-bands, and assume a blue 

 colour with iodine, are not, as appears at first sight, single grains 

 of starch, but are composed of globular heaps of some six starch- 

 granules crowded together. These are therefore comparable to 

 the compound starch-granules which occur abundantly in the 

 chlorophyll-granules of the interior of leaves and inner layers of 

 bark, unless it be preferred, for which however there does not 

 seem to me to be any reason, to regard them as chlorophyll- 

 granules, imbedded in a green mucilaginous layer here divided 

 into spiral bands. 



The chlorophyll-bands undergo most remarkable alterations 



