36 



Mr. J. R. Green. 



[Jan. 14, 



bulk of this extract was added, and a similar quantity of the same 

 was added, in another vessel, to as much water as the quantity of the 

 profceid solution taken. The two were submitted to a temperature of 

 40° C. for twenty-four hours. The biuret test was then applied to 

 both, care being taken to have equal quantities taken, and the same 

 amount of caustic soda and copper sulphate added to each. Peptone 

 was shown to be present in both, but the colour was the deeper in the 

 case of the proteid solution. Hence, though a trace of peptone was 

 present in the juice employed, the experiment showed formation from 

 the proteid in the latex. 



All the material investigated so far had been taken from the plant 

 a considerable time before being examined ; also a certain but varying 

 amount of alcohol had been mixed with it. There was consequently 

 a double possibility of decomposition of some sort having taken place. 

 In one case at least there was no doubt that a certain portion of the 

 proteid had been coagulated. It seemed desirable therefore to in- 

 vestigate certain plants that could be obtained in fair quantity in the 

 fresh condition, and as laticiferous tissues were those in which most 

 proteid matter would be found, choice was made of Manihot glaziovii 

 Muell. Arg. (Euphorbiacece)* and the common lettuce, Lacbuca sativa, 

 L. (Oompositce). A considerable number of the young plants of the 

 former of these was kindly raised by Mr. Irwin Lynch, at the Botanic 

 Garden, Cambridge, and on their attaining a height of about 10 feet 

 they were cut down and examined. On wounding them a milky latex 

 exuded, but it was impossible to get this to flow in sufficient quantity 

 to work with, hence another method of extracting it proved necessary. 

 The young plants were cut down, their stems taken and freed from 

 leaves and branches, and the cortex scraped off by a blunt knife. The 

 mass of tissue was then finely minced, pounded in a mortar, and put 

 into a quantity of water just sufficient to cover the pulp. After 

 standing for twenty-four hours the whole was strained in a press 

 through a coarse cloth, yielding a nitrate, turbid, and full of small 

 particles of debris, chlorophyll granules, &c. In quantity it was 

 about twice the bulk of the water used ; this solution therefore was 

 diluted latex, containing also any soluble matter originally present in 

 the parenchymatous tissue of the cortex. Filtration, repeated many 

 times, freed it ultimately from all colouring matters and debris 

 arising from the preliminary treatment. Any soluble proteid existing 

 temporarily or permanently in the tissue was hence in this extract. 



The proteids normally present in the sieve tubes of Manihot have 

 not been determined, but it is fair to assume that they do not materi- 

 ally differ from those of Gucurbita. From these Zachariasf has found 

 it possible to extract a proteid body which behaves like a globulin. 



* [The commercial source of Ceara rubber. — W. T. T. D.] 

 f " Bot, Zeitg.," February, 1884, p. 67. 



