1916] DISEASES OF PLANTS. 545 



The work begun by the department of plant pathology some years ago in de- 

 veloping resistant strains of cabbage has resulted in the establishment of such 

 strains and the production of a considerable amount of seed for testing in 1916. 

 Trials made in different regions indicate that the disease-resistant quality is 

 maintained even in widely different localities. In connection with this disease, 

 J. C. Oilman has observed that the growth of the parasitic organism causing it 

 is greatly increased at temperatures above 64°. This, it is believed, will explain 

 why the disease is so much more serious in some seasons than in others, and 

 also indicates that it will not be so severe in the northern as in the southern 

 parts of the State. 



Some observations on pea blight were continued, and the former recommenda- 

 tions of careful preparation of seed bed and attention to drainage are repeated. 

 For the disposal of the refuse vines the use of silos is suggested. 



Some investigations had been begun on cucumber diseases, of which wilt, an- 

 gular leaf spot, anthracnose, and scab are said to be due to definite parasites, 

 while a fifth, white pickle or cucumber mosaic disease, is not known to be due 

 to any organism. These five diseases are said to be more or less serious in 

 Wisconsin. The white pickle or cucumber mosaic disease is characterized by 

 irregular malformed fruits which are usually worthless for pickling purposes. 

 The trouble is considered transmissible, but as yet no parasite has been discov- 

 ered. Similar conditions have been found to obtain with squash and watermelon, 

 from which the disease may be transferred to the cucumber. 



Studies on the crown gall of plants. Its relation to human cancer, E. F. 

 Smith (Jour. Cancer Research, 1 (1916), No. 2, pp. 231-309, figs. 92). — The 

 present paper, which reviews certain of the essential features of crown gall, 

 especially as they bear upon the general problems of cancer, also contains a 

 number of new observations which are considered to bring this vegetative 

 growth into relations with the group of tumors described as embryomata. 



The author calls attention to the growth without function exhibited by the 

 crown gall tumors, the cell itself being properly regarded as parasitic only in 

 the sense that it is urged on by a schizomycete, Bacterium tumefaciens, and to 

 the embryonic character of the proliferating tumor cells. Attention is called 

 also to the atypical arrangement of the tissues, to their loss of polarity, and 

 to the slight differentiation of the cells accompanying their increase in vege- 

 tative vigor. The neoplastic character of the growths is emphasized by the 

 noncapsulate marginal growth, the imperfect vascularization, the early central 

 necrosis, the existence of intrusive strands, and the occurrence of daughter 

 tumors, which reproduce the original tumor. The same micro-organism is ca- 

 pable of producing by inoculation different types of tumors varying in structure 

 according to the type of tissue invaded, the most complex type containing, along 

 with blastomous elements, a jumbled and more or less fused mass of embryonic 

 organs and fragments of organs comparable, if not equivalent, to the foetal or- 

 gans occurring in the atypical animal teratoids. 



The distribution of black rust in Norway, E. Henning (Meddel. Centralanst. 

 Forsoksv. Jordbruksomrddet, No. 107 (1915), pp. 16; K. Landtbr. Akad. Handl. 

 och Tidskr., 54 (1915), No. 2, pp. 122-135; abs. in Bot. Centbl., 128 (1915), No. 

 18, pp. 495, 496). — It is thought that the barberry was introduced into Scandi- 

 navia at least as early as the beginning of the seventeenth century, and black 

 rust of wheat (Puccinia graminis) not later than the eighteenth, and possibly 

 in the seventeenth, century. Since this time the barberry has been used as al- 

 ternate host, both barberry and fungus being more successful in the middle and 

 southern portions than in the north, where the rust has little economic 

 impcrtance. 



