Comparative Study of Clilorophyll. 415 



change must have occurred in the chlorophyll since its 

 extraction, or benzol would not take up in one case a yellow, 

 in the other case a blue, colouring-matter. What brings 

 about this peculiar change is probably the addition of water 

 to the alcoholic extract ; and I believe that if we could 

 extract chlorophyll by absolute alcohol, avoiding the presence 

 of water, the above-mentioned decomposition would not 

 occur. For the same reason I believe extracts made by 

 triturating healthy material with substances similar to benzol 

 to be superior to extracts made by absolute alcohol. The 

 great disadvantage, however, of triturating is that only small 

 quantities of chlorophyll can be extracted. 



The conclusions which I have arrived at from microscopic 

 and spectroscopic investigations are shortly these : — 



1. Chloroplasts consist of an individual green proto- 



plasmic ground-substance, which is rendered 

 spongy by the presence of an oily material 

 secreted by the ground-substance, and which is 

 enclosed in a clear protoplasmic envelope. 



2. The fatty or oily material in Spirogyra is partly 



given off directly into the surrounding protoplasm, 

 partly consumed by the ground-substance. 



3. Chlorophyll does not consist of a mixture of a yellow 



and blue colouring-matter, but is a green sub- 

 stance, which readily decomposes into a yellow 

 and blue colouring- matter. 



4. Tlie first absorption-band of Kraus really consists of 



two bands. The fourth band of Kraus is in all 

 probability a decomposition-product, and hence 

 the absorption-spectrum of living chlorophyll is 

 the following: — 



Band 1 = X 686-69 -X 661-5 \_ 



Band 2 = X 656-86 -X 640-93 i "^^^"^ "^^"^ ^• 



Baud 3 = centre at X 616-6 = „ „ 11. 



Band 4 = centre at X 578 = „ „ III. 



Band 5 = X 514-9 -X 460-9 = „ „ V. 



•Band 6 = X 452 -X 440-75 = „ „ VI. 



