944 



ISCIENCE. 



[N. S. Vol. XXI. No. 547. 



parts and to the developing seed is most 

 remarkable. The production, whether 

 regulatory or otherwise, of the numerous 

 by-products in the cell, such as tannin, pig- 

 ments, organic acids, etc., is also of pe- 

 culiar interest. The functions of some of 

 these compounds must be most important, 

 and should receive further attention. Tan- 

 nin, particularly, is doubtless of much 

 economic importance in the regulation of 

 turgor and in augmenting the resistance to 

 injurious external agents. Astruc has re- 

 cently shown that acids are found in the 

 younger parts of non-succulents and mostly 

 in the region of maximum turgescence ; 

 and that there is a progressive decrease of 

 such compounds in the older organs. In 

 succulents, moreover, very slight changes 

 in the external conditions materially affect 

 the acid content. 



It can not be expected that all of the 

 information desirable with relation to the 

 composition and action of hydrolyzing and 

 oxidizing enzymes will be obtainable until 

 more is known of the proteids, to which 

 group the ferments seem to belong, or with 

 which they are at least closely related. 

 Whether these enzymes are concerned with 

 the metamorphoses involved in rendering 

 soluble or transforming pectin, proteids, 

 giueosides, starches, cellulose, fats, or 

 sugars, their physiological activities are in 

 the highest degree remarkable, and worthy 

 of the closest study. The problems which 

 relate to their occurrence, composition, 

 production and action require, however, 

 the combined attention of physiologists and 

 organic and physical chemists. In recent 

 times, through the work of Brown and 

 Morris, Fischer, Green, Prescott, Vines, 

 Loew, Beijerinck, Newcombe, Woods, and 

 many others, these compounds have re- 

 ceived renewed attention. It may be that 

 at present too many obscure phenomena 

 iire passed over with the superficial expla- 



nation that they are the result of enzyme 

 action, and, therefore, require no further 

 consideration. It is known that the fer- 

 ments are largely concerned with the regu- 

 latory production of modification of nu- 

 merous metabolic products. The activity 

 of each enzyme is circumscribed, yet the 

 power to do work borders upon the miracu- 

 lous. It is asserted that invertin may in- 

 vert 100,000 times its volume of cane sugar, 

 and pepsin may transform 800,000 times 

 its volume of proteids. The chemist is 

 especially concerned with the composition 

 and occurrence of these, but the physiolo- 

 gist is interested not alone in the occur- 

 rence and specific action of the enzymes, 

 but also with the effects upon the general 

 metabolism of the individual plant, with 

 the methods and conditions regulating the 

 secretion of these products, and with their 

 vitalities or limiting external conditions. 

 Ferments may be concerned with external 

 cellular digestion, that is, with the solution 

 and absorption of foodstuff's from without, 

 thus necessitating exosmosis, or with intra- 

 cellular modifications, preparatory to the 

 direct use of the substances modified in 

 metabolism or in translocation. Again, 

 the ferments may be present only at a cer- 

 tain definite period in the life of a cell, 

 produced, undoubtedly, by special require- 

 ments and special stimulation. 



When isolated, or at least when outside 

 of the cell, many enzymes are most active 

 at temperatures far above those which may 

 be maintained within the living cell. An 

 explanation of this fact is difficult. Com- 

 parative studies of their reactions to light, 

 heat, toxic agents and other stimuli should 

 be made. In the penetration of parasites, 

 cellulose-dissolving ferments are important, 

 but further information is needed before it 

 can be said that the presence or absence of 

 such enzymes to any great extent affects 

 the resistance of certain varieties and spe- 



