254 Journal of Agricultural Research voi. xiii. No. 4 



excessive moisture (ij) or abnormally high temperature {14), coordi- 

 nated with a reduced assimilatory activity occasioned by weak illumina- 

 tion. The same factors are employed by various other investigators, 

 including Atkinson (i), Prillieux (6), Noack (5), Trotter (/6), and 

 Steiner (13), in explanation of the cause of intumescences. 



In contrast with this explanation is that of Viala and Pacottet (77) 

 and Dale (2), who maintain that brilliant illumination, together with a 

 moist atmosphere, is to be regarded as the ultimate cause. 



K lister (4) expressed the opinion that the introduction of poisonous 

 substances may be a cause of intumescences and that they are mani- 

 festly related to insect galls. The poison for the development of these 

 galls, he believed, was produced by the gall-forming insect. A review 

 of literature upon gall formation, a matter beside the present purpose, 

 and a rejection of the theory that galls result from the injection of a 

 chemical substance by the insect, are contained in a recent paper by 

 Rosen (7). 



The production of intumescences upon cauliflower as a result of the 

 stimulatory activity of copper compounds applied as sprays has been 

 demonstrated by Von Schrenk (8) and has subsequently been confirmed 

 by Rosen (7) and by Smith (ii). In explaining their proximate cause, 

 Von Schrenk maintains that the stimulatory activity is probably due 

 to high osmotic tensions resulting from compounds of the copper salts 

 with the protoplast. 



Smith's concept of overgrowths, particularly of crowngall and malig- 

 nant tumors, as expressed in recent papers {10, 11), is that they are due 

 to the removal of normal growth inhibitions. He found that various 

 substances — namely, aldehyde, acetone, alcohol, acids, and alkalies — 

 removed these inhibitions, not by direct chemical action, however, but 

 by locally increasing the osmotic pressure; hence, by physical action. 

 In the case of crowngall, various soluble substances were found to result 

 from the metabolism of the parasite in culture. If, as he contends, 

 these substances are slowly and continuously supplied by the intracellu- 

 lar growth of the organism, they would lead to osmotic disturbances 

 which would tend to be equalized by the movement of water and dis- 

 solved foodstuffs toward the parasitized cells. 



Fischer (5), to whom reference has previously been made, relates the 

 cause of swellings of animal tissues which manifest themselves in states 

 known as edema, glaucoma, and nephritis to the phenomenon of absorp- 

 tion both of water and of dissolved substances. The cell colloids and 

 their state, according to this theory, determine the amount of water 

 held by a cell, a tissue, an organ, or even the entire individual under 

 different physiological and pathological conditions. The cause, then, 

 of normal absorption, and consequently of abnormal absorption, resides 

 within the cells themselves. The nature and cause of edema can most 



