DISEASES OF PLANTS. 267 



ties of plants, describing what has been done in different parts of the world to ol)tain 

 resistant varieties of grapes, wheat, cotton, coffee, potatoes, cowpeas, sugar (!ane, and 

 violets. 



Frost injuries to cereals in relation to fungus diseases, P. Sokauer {Landv. 

 Jahrh., 3i3 {1903), No. 1, pp. 1-6S, pis. 4, fig- I)- — On account of the unusual occur- 

 rence of fungus diseases of cereals during a season following a number of severe late 

 frosts, a series of experiments was undertaken to ascertain the effect of frost and its 

 relation to fungus diseases of cereals. Tlie mechanical effect and physiological 

 changes caused by freezing are described at I'onsiderable length. 



Inoculation experiments with quite a number of parasitic fmigi upon frost-injured 

 jtlants and the effect of different times and conditions of seeding are reported upon. 

 The author found certain injuries that could be attributed only to frost injury, but 

 which resembled in their characteristics certain fungus diseases. Such, for instance, 

 is the state of cereals known as blast, white heads, etc. Serious injury due to frost 

 may be observed that in its earliest stages does not present any fungus mycelium, but 

 later parasites may attack the plants. There are some fungi now lielieved to be obli- 

 gate i^arasites which occur on sound healthy plants as well as upon those whose 

 organs have become weakened from any cause whatever. The presence of some of 

 the less active parasitic forms may be due to frost or other injuries in offering oppor- 

 tunity of entering the tissues of the host. 



Care in sowing somid seed, although desirable and tending to reduce the amount 

 of disease, will not wholly eliminate diseases in every case. Some wild grasses are 

 hosts for some of the more destructive fungi of cereals, and their presence on these 

 grasses may serve as a center to spread the infection. Plants weakened from any 

 cause whatever are more subject to serious injury than healthy ones. 



Preliminary observations on disease of cereals in Tunis, F. Bceuf {Bui. Dir. 

 Ayr. et Cum. ITunis], S {1903), No. 27, pp. 185-193, fi<ji<, 5). — The author describes a 

 number of diseases which have appeared on wheat, barley, and oats in Tunis, and 

 gives the results of determinations of the fungi which have been made at the Colo- 

 nial School of Agriculture. The fungi present were Erysiphe graminis, Puccinia ruhigo- 

 vera, P. graminis, Septoria, tritici, Sphssroderma darnnosum, and Cladosporium herbarum. 

 The princii^al injury seems to be caused by the Spha^roderma, and its ajspearance on 

 the different plants is fully described. The development of the diseases, the influ- 

 ence of soil humidity and temperature, etc., are pointed out. 



On the specialization of Erysiphe graminis, E. Marchal {L'Ing. Agr. Gem- 

 bloiLv, 13 {1903), No. 10, lyp. 457, 458). — In continuation of the previous jiaper on this 

 subject (E. S. R., 14, p. 667), the author reports that as a result oi further inoculation 

 exj^eriments he is convinced that there are definite forms of this mildew wliich are 

 specialized upon certain cereal host plants. 



Experiments for smut prevention, D. N. Pryanishnikov {Klwzyain, 1902, No. 20, 

 pj). 647-652; ahs. in Zlnir. Opuitn. Agron. [Jour. Expt. Landw.'], 4 {1903), No. 1, 

 p. 112). — The results are summarized as follows: Soaking during 12 hours in 0.5 per 

 cent solution, or 6 hours in 1 per cent solution of copper sulphate, completely destroyed 

 the snmt. Soaking for 5 or 10 minutes in 0.125 ])er cent solution of formalin is insuf- 

 ficient; greater concentration should be tried (according to David an hour's soaking 

 is re(|uired in 0.125 per cent solution). Formalin vapors applied in sullicient c(uan- 

 tity destroy the smut, but when applied to large quantities of grain it is diliicult to 

 cause the vajiors to thoroughly permeate the interior of the mass. 



As to the influence of the different kinds of soaking on the germination of wheat, 

 the experiments showed that 0.5 per cent solutions of copper sulphate is endured with- 

 out great harm (after 12 hours soaking 91 per cent of the seeds germinate), while solu- 

 tions exceeding 0.5 per cent are not suital)le for protracted soaking. (1 jier cent 

 solution lowered the germination to 66 jjer cent.) — r. fireman. 



Combating oat smut, H. Romjiktin {.four. Agr. Prat., n. ser., 6 {1903), No. 31, 



