No. 3, Decbmbeb, 1920] PATHOLCH.^ 187 



rents and plant foods on the disease. The question of susceptibility of varieties is treated 

 at some length. Forty-five varieties of bush beans were tested. It was found that in one 

 locality a variety might be relatively immune, while elsewhere it might be quite susceptible. 

 — .1. J. Fitters. 



12SG. Schultz, E. S., and Donald Folsom. Transmission of the mosaic disease of Irish 

 potatoes. Jour. Agric. Res. 19: 315-337. PL 49-56. 1920.— Tubers from mosaic hill- may be 

 expected to transmit the disease. Tubers from apparently healthy plants growing near dis- 

 eased plants also transmit the disease, at least in part. The tendency to do this is greater 

 when there are only 2 or 3 tubers on the plant, when the relal ive size of the tuber in the par- 

 ent hill is greater, and when the seed piece is near the "bud" end.— Transmission of the 

 disease was effected by grafting, by transfer of juice, and by means of aphids, the experiments 

 being carried out under various conditions, including field conditions, with test plants under 

 screened cages. Interparietal transfer of expressed juice from diseased plants to healthy 

 gave infection. "Transmission was attempted, but without success so far as could be ascer- 

 tained, in the same season, by means of flea beetles, Colorado potato beetle, the 'seed'- 

 cutting knife, and contact of seed pieces, of roots, and of vine." Infection probably does not 

 result from growing plants in soil on which diseased plants were produced the previous 

 year. "It appears impossible either for affected plants to recover or, so long as diseased stock 

 is not far off and insect carriers exist, to assure the maintenance of health of susceptible vari- 

 eties by rogueing plots or by selecting hills, tubers or seed pieces." Control of insect carriers 

 seems to be the important means of checking spread of potato mosaic. — D. Reddick. 



1287. Subramaniam, L. S. A Pythium disease of ginger, tobacco and papaya. Mem. Dept. 

 Agric. India (Bot. Ser.) 10: 181-194. PL 1-6. 1919.— See Bot. Absts. 6, Entry 784. 



1288. Suematsu, N. On the artificial culture of Helminthosporium Oryzae. Bot. Mag. 

 Tokyo 33: 291-297. 3 fig. 1919.— See Bot. Absts. 6, Entry 785. 



1289. Tubeuf, C. von. tiberblick fiber die Arten der Gattung Arceuthobium (Razou- 

 mowskia) mit besonderer Berucksuchtigung ihrer Biologie und praktischen Bedeutung. [Re- 

 view of the species of the genus Arceuthobium (Razoumowskia) with especial reference to their 

 biology and practical importance.] Naturw. Zeitschr. Forst- u. Landw. 17: 167-271. Fig. 1- 

 50. 1919.— The author calls attention to the number and size of witches'-brooms caused by 

 mistletoe occurring on most of North American species of conifers. It may be said that the 

 formation of witches'-brooms is the most extensive and apparent manifestation of disease 

 exhibited by North American Abieteae. Witches'-brooms on Cupresseae and Taxodium are 

 not caused by Arceuthobium. Witches'-broom formations resulting from Arceuthobium may 

 take place on all host plants. The root formation resembles that of Viscum alba, the Euro- 

 pean mistletoe, but that of Arceuthobium is more extensive than either Loranthus europeous 

 or Viscum alba. The type of growth depends on the species of Arceuthobium and the host. 

 The smaller species of Arceuthobium usually attack thin barked tree species; they develop 

 in dense clusters and form thick brooms where young shoots and buds are present. The larger 

 species occur chiefly on thick barked tree species; and although they do not exhibit the regular 

 progress of the root system of the smaller varieties, they can develop a large system, and 

 cause enormous thickening (hypertrophy) of infected branches. Infection by mistletoe most 

 commonly takes place on 2-3 year old shoots; rarely on shoots older than 5 years. It may 

 be supposed that the bark roots of Arceuthobium penetrate the first year growth the first fall. 

 A more complete study of physiological characters and extent is desired of the American 

 species. The various forms of Arceuthobium witches'-brooms are summarized. — The 13 well- 

 known species in America and in the Old World, and the characters of the three less well known 

 species in Mexico are tabulated, and each species is separately described with especial refer- 

 ence to host plants.— The biology of fruiting, seed distribution, germination, root and sucker 

 formation, and of the sprout are discussed at length; reference being made to investigations 

 of Heinricher, Peirce, MacDougal, and others. Pollination of European mistletoes is 

 effected by flies and by wind, the pollen grains being caught in a drop of nectar or oil (Heix- 



