DISEASES OF PLANTS. 547 



A series of cooperative experiments is reported upon in which seed tubers 

 sufficient to plant 142 acres were treated, formaldehyde solution being used 

 for those required for planting 88 acres and formaldehyde gas for 54 acres. 

 The results as a whole indicate that preventive measures are exceedingly 

 efficient. Where the seed tubers were selected and treated the disease was 

 absolutely eliminated, and where the seed was treated with formaldehyde solu- 

 tion or gas there was considerable reduction in the proportion of diseased 

 tubers. 



Field observations extending over 5 years indicate that the disease is not 

 carried over in the soil, but is transmitted by the tubers. 



It is recommended that tubers, where used for seed purposes, be treated with 

 formaldehyde, the solution being used where small quantities are to be treated, 

 and the gas where the treatment is to be made by seed dealers or others who 

 have a considerable amount of stock to be grown. Observations made in the 

 cooperative experiments des(?ribed above showed that the treatment did not 

 affect the vigor of plants when properly applied, nor was there any indication 

 of a stimulating effect similar to that attributed to etherization. The result 

 of better stand and growth is attributed to the freeing of seed pieces from bac- 

 teria and fungi which might attack them and set up an early decay. 



On tumor and canker in potato, A. S. Horne {Jour. Roy. Hort. Soc, 37 

 (1911), No. 2, pp. 362-389, j)ls. 9). — A discussion is given as to the proper 

 identification of the fungus causing the black scab or tumor of potatoes, and 

 attention is called to the apparent fact that 2 diseases, one caused by 

 Chrysophlyctis endoMotica and the other by Spongospora solani, are very com- 

 monly confused. The author believes from the evidence at hand that the trans- 

 fer of Chrysophlyctis to Synchytrium is not warranted. For the disease due 

 to Spongospora the name potato canker is preferred, and for the other disease 

 potato tumor or black scab is considered the more distinctive name. 



A bibliography of the subject is appended. 



Bacterial fibrovascular disease and leaf-roll disease of the potato, A. 

 Spieckkrmann (Jahresher. Ver. Angew. Bot., 8 {1910), pp. 1-19, 173-177 ; abs.m 

 Centm. Bakt. [efc], 2. AM., 31 {1911), No. 23-25, pp. 598-600).— This is an ex- 

 tension of previous work (E. S. R., 23, p. 744) in which the author after review- 

 ing briefly work previously done and the views lield by others in regard to the 

 relations of these 2 diseases presents details of his own later investigations 

 as to the migration of material from the tuber during the vegetative period, the 

 results of which may be briefly stated as follows : 



As regards consumption of organic materials no differences were observed be- 

 tween the diseased and the sound plants. On the other hand, the ash material 

 was carried more rapidly and completely from the tubers of sound than from 

 those of diseased plants to the above-ground portions. Nevertheless, the ash 

 content of the above-gi'ound portion of diseased plants was higher than that of 

 the sound plants. The transfer of nitrogen compounds was less rapid and less 

 complete in case of sick than of sound plants, and the nitrogen content of the 

 above-ground portions of sound plants was greater than that of diseased ones. 

 The simplest explanation for the persistence of the diseased seed tubers is that 

 in plants which produce limited quantities of dry substance the salts and nitro- 

 gen compounds of the seed potatoes can not be utilized, and, therefore, these I'e- 

 main in the sick tubers, which thereby can survive longer. 



Biochemical researches on the leaf-roll disease of the potato. — II, The 

 oxidases of resting' and sprouted tubers, G. Doby {Ztschr. Pflanzenkrank., 

 21 {1911), No. 6, pp. 321-336, figs. 5).— Continuing investigations on the leaf- 

 roll disease of the potato (E. S. R., 24, p. 552), the author claims to have found 



