56 CARNEGIE INSTITUTION OF WASHINGTON. 



new joints of opuntias. It was therefore necessary to use joints of the previous 

 year's growth. 



One of the first methods of extraction attempted was by shcing the joints 

 and drying first in the air and then in vacuo over H2SO4, grinding, and extrac- 

 tion in a large Soxhlet, first with ether and then with alcohol under reduced 

 pressure. The ether extract contained chlorophyll and probably some true 

 fats along with the phosphatides and their decomposition products, and the 

 alcohol extract contained some chlorophyll and rather large amounts of 

 carbohydrate. However, the small quantities that could be handled did not 

 permit satisfactory purification of the phosphatides. 



The fresh material was also sliced and extracted immediately with distilled 

 water according to the method of Cranner.^ By this method a large number 

 of phosphatide fractions were obtained, which all gave glycerine, fatty acids, 

 chlorine, and phosphoric acid as the hydrolysis products. Carbohydrate was 

 very evident in some, and was probably present in all. Some of the fractions 

 were obtained in sufficient quantity to allow proof of both saturated and 

 unsaturated fatty acids, but in no case was a product obtained which seemed 

 pure enough to warrant a quantitative analysis. In one attempt, complete 

 precipitation of the phosphatide from the original aqueous solution was 

 obtained, but attempted repetition was not successful. If this method could 

 be perfected, the aqueous extraction might be practicable; otherwise the yield 

 of phosphatide is seriously limited by the large amount of water to be 

 removed. 



The method devised by MacLean ^ for the extraction of lecithin proved 

 fairly successful if very large quantities of material were available. In some 

 of the earlier attempts with this method , a lecithin-like substance was obtained 

 which contained 1.26 per cent N and 2.77 per cent P. Considerable carbo- 

 hydrate was present. In the latest attempt (in which the product was dis- 

 solved in ether and reprecipitated by acetone five times, then emulsified in 

 water and precipitated by acetone five times) the resultant product gave 1.54 

 per cent N and 3.31 per cent P. Some carbohydrate was still present. 

 Whether this is actually chemically combined (perhaps loosely), or merely 

 physically entangled, is a matter of conjecture. The need of further work is 

 very apparent. 



ECOLOGY AND PHYTOGEOGRAPHY. 



Experimental Investigations on Roots, by W. A. Cannon. 



The physiology of roots has been subject to investigation in this Depart- 

 ment for several years, during which time the general problems connected with 

 activities of roots have been outlined, special methods of attack have been 

 developed, and especially designed apparatus has been used, with the investi- 

 gations carried on pari passu. The lack of organized and systematic work on 

 the physiology of roots, despite the evident importance of the subject, 

 enhances the value of such researches. 



The ultimate aim of the investigations is to acquire data which will define 

 as clearly as may be practicable the role played by the root in the activities 

 of the plant as a whole. Logically, therefore, the scheme implies studies at 



^ B. Hansteen-Cranner, Zur Biochemie und Physiologie der Grenzschichten lebender Pflanz- 

 enzellen. Meld. f. Norges Landbrukshoiskole 1.1-160. 1922. 

 * Hugh MacLean, Lecithin and allied substances. Monograph on Biochemistry (1918). 



