648 EXPERIMENT STATION RECORD. 



rust fungus (G. juniperi-virglnianw) are given. The studies were made on two 

 varieties of apples, York Imperial and Ben Davis, and twigs and leaves on 

 the trees in their natural position were studied. 



It was found that the transpiration of the diseased leaves of both varieties 

 of apples was in most cases less than that of the healthy ones. The percentage 

 of M^ater transpired by diseased leaves during the period of the experiment 

 was 78.3 per cent for York Imperial and 72.4 per cent for Ben Davis, as com- 

 pared with that of normal leaves. 



It is believed that the hypertrophy of the leaf and the subsequent oblitera- 

 tion of intercellular space diminishes the possibility of water elimination from 

 the interior of the leaf. The retardation of transpiration by the fungus is 

 considered to have some significance in the study of the problems pertaining 

 to this disease, as assimilation is diminished whenever the transpiration stream 

 is reduced. 



The effect of the cedar rust upon the assimilation of carbon dioxid by- 

 apple leaves, H. S. Reed and J. S. Cooley {Virginia 8ta. Rpts. 1911-12, pp. 

 / 01-94, fid- !)• — By means of a Ganong photosynthometer the authors studied the 

 carbon dioxid assimilaton of leaves of York Imperial and Ben Davis apples 

 during the summers of 1911 and 1912. It was found that the average rate 

 of assimilation in diseased leaves was only about one-half that of normal 

 healthy leaves, the two varieties giving almost identical results in this respect. 



The fungus is said to modify the parenchyma of the leaf to such an extent as 

 to interfere with gaseous exchange and also to diminish it by the obliteratibn 

 of the stomata through the hypertrophy of the leaf. 



The enzym activities involved in certain fruit diseases, H. S. Reed {Vir- 

 ginia Sta. Rpts. 1911-12, pp. 51-77). — An account is given of studies upon the 

 enzyms produced by Glomerella rufomacuJans, the fungus which causes the 

 bitter rot of apples, and also on the action of the enzyms upon the host plant. 



It was found that the fungus produced several enzyms, such as amylase, 

 invertase, cytase, and inulase, which act upon carbohydrates. Zymase appeared 

 to be lacking. Emulsin was found to be entirely an intracellular enzym. Lipo- 

 lytic enzyms were present and fairly active. The fungus produced several 

 enzyms which act upon proteins and their constituents. Among them protease, 

 erepsin, and amidase were demonstrated. The presence of an enzym which 

 splits hippuric acid into glycocoU and benzoic acid was also demonstrated. 

 The enzyms appear to possess the ability to break down certain important 

 constituents of the tissues upon which the fungus grows. The juice of decayed 

 ajiples was found less suited to the growth of the fungus than that of sound 

 ones of an equal sugar content. The poorer growth of the fungus on the juice 

 of the decayed apples is thought probably due to the higher tannin content. 

 The fungus during its growth on the substratum seems to bring about an 

 alkaline condition. 



Studies on Phyllosticta and Coniothyrium occurring on apple foliage, 

 C. H. Cbaeill (Virginia Sta. Rpts. 1911-12, pp. 95-115, figs. 16).— A study of 

 these two fungi in connection with the frog eye spot of apple leaves is reported. 

 Investigators have considered different fungi as causing this disease, and a 

 detailed report is given of the author's investigations on the life history of 

 these two fungi and the results of inoculation experiments. 



From his experiments the author claims that G. pirinum and P. pirina are 

 radically different in the color of spores, germination, and cultural characters, 

 and that each species is composed of more than one strain or subspecies. These 

 strains, with one exception, are very much alike in moiT)hological characteris- 

 tics and they come true to type from generation to generation. The growing 

 of any two strains together showed no tendency to sexual reproduction. None 



