600 BACTERIAL DISEASES OF PLANTS 



. with some other facts, already detailed in the preceding chapters, 

 and may help to throw light on the mechanism of the response, 

 and also, perhaps, on the origin of animal teratomas and of 

 certain cancerous phenomena. 



23. First, let us try to conceive what takes place in the 

 plant when it is suddenly deprived of a part of its roots by 

 cutting or breaking, while others cease to function, owing to 

 loosening of the previously compact earth. One thing at least 

 happens with certainty, there is a sudden marked diminution of 

 the very considerable water-supply necessary for the well being 

 of the plant. The plant is transpiring more or less freely over 

 a broad leaf surface (several square feet) and suddenly it is de- 

 prived of its water-supply. This, I believe, is the shock which 

 starts the dormant totipotent cells into development. It is 

 impossible that the plant should wholly cease to transpire. 

 Since it must breathe to live, water will escape from its stomata 

 and lenticels, and it seems likely that the thin- walled, immature 

 and delicate tissues of the terminal buds will be just the ones 

 from which proportionately most water will be abstracted to 

 meet this unusual demand and which will be most shocked by 

 the loss they sustain. That the plants lose water in ex- 

 cess is demonstrable by the balances. Other phenomena also 

 occur but these are secondary results, e.g., there is sometimes 

 slight wilting especially in cuttings, growth above-ground 

 ceases for a short time and the elaborated food that would 

 have been used for further extension of normal shoots is sent 

 downward to make new roots. The aeration of the interior must 

 also be less perfect than it was since the absorbed water always 

 carries dissolved air. Less oxygen, therefore, will reach the 

 tissues, and, theoretically, they should become more acid than 

 normal.^ 



^ Subsequently I tested the terminal buds of 42 plants of Series VI with the 

 following results: 



A. I. 21 tops (bearing 4-5 leaves) cut from the plants and dried 48 hours at 

 28°-30°C. on a laboratory table (July 12-14, 1919) in diffuse light: 



1. Fresh w^eight, 740.25 grams. 



2. Loss of weight in 48 hours, 191.50 grams. 



3. Juice of the 21 buds crushed at end of the 48 hours, extracted 10 minutes in 

 hot water (90°C., falling to 35°C.), squeezed dry in a hand screw-press and filtered : 



