450 EXPERIMENT STATION RECORD. [Vol. 38 



supply by the fun{?iis; increased transpiration clue to a rise in temperature; 

 and the possible production of toxins which injure the host protoplasm. 



As a result of the studies on resistance, it is believed that resistance is es- 

 sentially of a chemical nature. Inheritance of resistance through hybridization 

 in which susceptible and immune strains were crossed was studied, and re- 

 sistance was found to be an inherited character which is apparently determined 

 by multiple factors. Great difference was observed in the individuality of 

 plants with respect to the resistant character, as shown by their offspring. 

 The first generation from some crosses is entirely resistant, from some inter- 

 mediate, and from others entirely susceptible. The degree of resistance appears 

 to depend to a considerable extent on the environmental conditions under 

 which the plants are gro^vn. Plants of North Dakota Resistant No. 114 were 

 found not entirely resistant under the high summer temperatures in the green- 

 house. 



In conducting experiments of this kind, the author suggests that all parent 

 strains to be used in crossing be thoroughly tested on infected soils under 

 unfavorable conditions before making crosses, and that hybridisation experi- 

 ments be conducted under uniform environmental conditions in order to obtain 

 conclusive results. 



On the resistance to fungicides shown by the hop mildew (Sphserotheca 

 humuli) in different stages of development, E. S. Salmon (Ann. Appl. Biol., 

 3 (1917), No. 2-3, pp. 93-96, pi. 1). — The experiments carried out on Erysi- 

 phacese, as previously noted by the author in connection with Eyre (B. S. R., 

 37, p. 47), were conducted on the assumption that the resistance of the fungus 

 to the fungicidal properties of a chemical would be highest when couidiophores 

 and conidia were most evident. Experiments by the autlior during 1916 with 

 hop plants, however, are said to have shown that the mildew growing on tlie 

 host plant is more difficult to kill when at an earlier stage of itJs development. 

 The details of two experiments are given. Evidence collected is said to indi- 

 cate that tlie age of the mildew, even when in tlie powdery conidial stage, is a 

 factor of importance, the older conidial patches showing less power of resistance 

 than the young patches to the soluble sulphid spray. Apparently the age and 

 condition of tlie leaf are to some extent concerned, the mildew on old hop 

 leaves having less resistance than on vigorous young leaves. Other factors are 

 thought to be involved. It still remains to be determined at what stage it 

 is most economical to employ the fungicide. 



Neck rot disease of onions, M. T. Munn (New York State Sta. Bui. JfSl 

 (1917), pp. S63-Jf55, pis. 11, fig. 1). — Under the name neck rot disease the author 

 describes an affection of onions known to occur in all the principal onion sec- 

 tions of the United States, where it causes heavy losses in stored onions and 

 frequently in the growing crop and the seed crop. 



The cause of the disease has been referred to a number of species of fungi, 

 but as a result of his studies the author claims that it is due to Botrytis 

 aim. The infection of the bulbs in the field is said to occur through the leaves 

 and necks, the fungus passing down the neck and causing a rot in the field or 

 else going into the storage house where the disease develops rapidly under 

 favorable conditions. The bulbs may also become infected from the soil and 

 the seed heads from wind-blown spores which cause a blasting of the flowers. 



As a result of his investigations, the author has found that the fungus pro- 

 duces appreciable amounts of oxalic acid, but no pathological effect of this acid 

 could be demonstrated. It was found, however, that pectinase was secreted, 

 and from a study of extracts of this material acting on plant tissue, a pos- 

 sible explanation was secured of the tissue changes taking place when the 

 parasite attacks the host. 



