882 



protecting cork is produced. Poorly nourished shoots produce no protect- 

 ing cork and on this account bear especially large and numerous bark warts. 

 These black specks, therefore, furnish a standard for judging the degree of 

 maturity of the wood and the health of the vine. The more numerous and 

 the larger they are, the less mature in general is the wood. 



Page 378. In Geisenheim, Julie Jiiger observed a wen formation of 

 the apple tree (Zeitschr. f. Pflanzenkrankh. 1908). The cause has not been 

 sufficiently determined, but is probably to be found in some disturbance of 

 nutrition, which manifests itself in the widening of the medullary rays. 

 Some medullary rays in their primordia show a greater cell increase and 

 widening of the individual cells. The process is connected with the forma- 

 tion of gnarl spikes from the medullary excrescences in Ribcs mijrum and 

 Pints mains chinensis, which we have described. 



Pages 391 and 395. The iron spotted condition of potatoes was unusu- 

 ally wide-spread in the wet year of 1907 and connected with it appeared a 

 yellow to brown discoloration in the vascular bundle ring. This discolor- 

 ation, in common with a frecjuent diseasing of the stem end, in which at 

 times a Fusarium was concerned, has influenced Appel to explain the 

 so-called leaf roll disease, a form of the curling disease, as a fungus epi- 

 demic. Appel maintains that the Fusarium, found at the stem end, grew 

 during the winter through the vascular bundle ring into the eyes of the 

 tuber and caused the following year an increased occurrence of the disease 

 and a gradual destruction of the potatoes. The same theory has been 

 advanced by Reinke and Hallier, only they have made another fungus 

 responsible for it. Sorauer proves (Internationaler phytopathol. Dienst, 

 Stiick 2, 1908) that the Fusarium, to be sure, may be found frequently but 

 that other slime fungi appear just as often; that all fungi could never be 

 observed to be growing in the vascular bundle ring of the tuber up to the 

 eyes. It is not a question of a fungous disease and its continuance through 

 the tubers into the following year. The phenomena of discoloration in the 

 tuber may rather be explained by the increase of the enzymes which Prof. 

 Gruss has proved to have accumulated especially about the stem end. Con- 

 sequently, a relatively larger amount of sugar w^ould be present, which 

 would form an especially favorable substratum for numerous micro- 

 organisms. 



Page 496. The influence of electricity on plant growth was tested at 

 the Hatch Experiment Station of the Massachusetts Agricultural College 

 (cit. Z. f. Pflanzenkrankh. 1908). Raphanus sativus was used ^s the experi- 

 mental plant. It showed a hastening of the rate of growth and an increase 

 in weight of foliage and roots; the leaves, however, were a lighter green and 

 • were inclined to leaf blight. The electric stimulus seems to act on the 

 organs in the same way as does a lack of light. 



Gassner (Berichte d. D. Bot. Ges., 1907, Part i) can confirm the results 

 of Lowenherz's experiments mentioned in the text. The curvature produced 



