DISEASES OF PLANTS. 761 



DISEASES OF PLANTS. 



Potato diseases, E. Roze (Gard. Ghron., 3. ser., 24 (1898), No. 608, 

 p. 134.) — The conclusions of the author as to the cause of various potato 

 diseases are given. He states that the dry rot is produced by Pseudo- 

 commis vitis, in which case the tubers are free from any odor, but show 

 depressed dark spots in the parenchyma with a brownish band sur- 

 rounding. These tubers can be kept until spring, when they develop 

 shoots which bear brownish or blackish tips. Dry rot may also be 

 produced by a species of Micrococcus. In the case of this form of 

 attack the tubers are said to be free from odor, moderately firm, more 

 or less soft in spots, but showing in certain places a loose epidermis 

 which yields to the pressure of the finger. Under this epidermis the 

 parenchyma exhibits white, gray, or brownish blotches. Sometimes 

 there are depressions which exhibit the sclerotia of Ehizoctonium or 

 later an abundant development of Fusisporium and Spicaria. 



The wet rot is produced by a species of Micrococcus closely allied to 

 Bacillus subtilis. The tubers are partly or wholly soft and exhale a 

 very disagreeable odor. Under the epidermis there is a disintegration 

 of parenchyma with an elaboration of butyric acid. Destruction is 

 slow and progressive and contact with healthy varieties should be 

 avoided. Wet rot is also said to be produced by Phytophthora infestans, 

 in which case there is a partial or complete softening of the tissue, the 

 epidermis is shrunken, the parenchyma which is weakened is depressed, 

 pasty, but not deliquescent. The author states that of the different 

 forms of potato rot at least 50 per cent of the tubers are attacked by 

 Micrococcus sp. and 25 per cent by the Pseudocommis, while a still 

 smaller amount is due to Phytophthora. 



The remedies recommended are alternation of crops, planting of 

 healthy tubers, destruction at harvest of all diseased potatoes, and 

 treatment of the plants with copper fungicides. 



Diseased potatoes, Gr. Abbey (Jour. Rort., 50 (1898), No. 2620, pp. 

 463, 464, Jig. 1). — Specimens of some badly infested tubers were sub- 

 mitted to the author for examination, and he reports finding in one of 

 them several wireworms and quite a number of small forms closely 

 related to the springtails. In another specimen several protuberances 

 of various kinds were noted, some just beginning, while others were in 

 a more advanced stage of development. No trace of animal life was 

 discovered in the cracks of the excrescences, which were black and 

 moist, the warts being brown and scabbed. A closer examination of 

 these tubers showed the presence of the scab fungus O'dspora scabies, 

 but the main trouble, the author states, could not be attributed to this 

 cause. A slimy fungus closely related to the Plasmodiophora was 

 present in abundance. It is stated that it may be Pseudocommis vitis, 

 although the resemblance is not sufficiently clear. Besides the various 

 parasites already mentioned there were found present Bacillus amylo- 

 bacter, the mycelium of Fusarium solani, a root worm (Enchytrceus 



