DisiCASKS OF^x'ARiou.- Cl<o^^^ 1037 



most resistant wheats have a different chemical composition from those of 

 low resistance, speak in favour of this hypothesis. 



In order to test this hypothesis, the author studied the acid content of 

 wheats differing clearly in their smut resistance. These were young plants 

 of the " Richmond giant wheat " (highly liable to the disease) and " Flirst 

 Hatzfeld " (highly resistant ) which are morphologicallj' identical. It 

 \ was found that the resistant plants concained more acid than the suscept- 

 i ible ones. The absolute difference is small, but deserves te be pointed 

 out, especially as the morphological characters of the conditions of growth 

 of the two plantlets were the same. It may therefore be concluded from this 

 experiment that there is a relation between the acid content and the re- 

 sistance to smut. 



810 - Variations in the Resistance of Vines to Mildew. — rav.\z ly. and OaiKDOFF.s. in 



/,(■ Proi^rc's a^ricoU' ct vilicolc, 33r(l Year, Nu. u), pp. 441-4 \7 , Fig. 1-6. Mfintpollitr, May 7, 



Though common to all vine varieties, the disease varies considerably 

 in intensity according to the variety. What is the cause of this differ- 

 ence of behaviour ? 



It is well known that the stomata are the only channel through wlaich 

 the hyphae of the parasite can enter. The writers, by a large number of 

 experiments, determined exactly the average number of stomata per unit 

 of surface of the leaf stems and petals of many kinds of vines, both 

 French and American, without discovering any relation between the degree 

 of resistance to mildew and the number of stomata. In any case the ratio 

 would if anything be inverse, as there is a relatively larger number of sio- 

 mata on the corresponding parts of American vines which are well known to 

 have a high degree of resistance, while French vines, very liable to the di- 



i sease, have fewer stomata. 



The degree of attack of the vines is to be explained rather by the more 



• or less early character of the types, and also the time when infection be- 

 comes apparent. When the leaf stems are very soft and herbaceous and 

 still in process of growth the disease develops rapidly, causing the axes of the 

 inflorescences to droop and partial rot of the tissues. Later on, on the other 

 hand, when the leaf stems are partially lignified they become highly 

 resistant. The fungus develops for preference on the young organs or on 

 those in course of growth, as for instance on newh formed flowers and 

 grapes. 



Nil - Morphology and Conditions of Development of the "Sclerotium Disease of 

 Clover" {Sclerotinia trifoliorum).-- peglion vittorio in Rendicovti ddic 



scduti- della Reulc Accademia dci Lined , Classe di Scicnze jisichc, malematichc e natural i, 

 Sth Series, Vol. XXV, ist Halt- Year, Part 7, pp. 321-524. Rome, April 2, 1916. 



Among other questions in connection with ScJerotinia trifoliorum. 

 which causes considerable damage to clover fields, especially in northern 

 Europe, no solution has yet been reached with regard to those concerning 

 the conidial or micro-conidial stage of this fungus and the conditions caus- 

 ing the epidemic outbreak of the disease in clover fields. The writer \\\\- 

 dertook the study of S. trijoliorum in order to solve these problems. 



DISEASES 



(II- VARIOUS 



CROPS 



