984 EXPERIMENT STATION RECORD. 



seeds and consequently a higher percentage of germination. While the total num- 

 ber of seeds germinating in the laboratory was higher than that observed in the 

 held, yet all the seeds germinating in the laboratory were not able to develop into 

 plants at all comparable with those produced in the open field. In the experiments 

 with alfalfa the highest germinations were obtained in the open air trials. 



Wild hemp or sesbania, W. H. Forbes {Arizona Sta. Rpt. 1904, PP- 494-496, figs. 

 2). — Notes are given on th» growth, habits, and possible uses of the wild hemp 

 I Seaborn macrocarpo). This is a leguminous plant very abundant in portions of Ari- 

 zona and lower California, and it is believed to be of value on account of the long 

 strong fiber borne in the stalks. The plant is also believed to offer considerable 

 promise for green manuring. 



Influence of chlorin water on germination, R. Spatschil (Oeslerr. Bot. Ztschr., 

 54 {1904), No. 9, pp. 825-329; abs. in Bot. Centbl, 9S (1905), No. 1, p. 9).— Soaking 

 the seed of Lepidium sativum and other oil-containing seeds, such as radish, mustard, 

 turnip, etc., in chlorin water for a short time was found to hasten germination. The 

 influence of the chlorin water seemed to be wholly exerted with the softening and 

 swelling of the seed coat, and it had no apparent effect on the subsequent growth of 

 the seedling. Soaking peas, corn, rye, barley, and oats for a short time in chlorin 

 water had a retarding effect on the germinative processes. 



DISEASES OF PLANTS. 



Specialization of parasitism in the Erysiphaceae, E. S. Salmon (New Phytol., 

 3 (1904), N'os. 2, pp. 55-60, figs. 3; 5, pp. 109-121). — In the first of these papers the 

 author reviews recent investigations on the specialization of parasitism among the 

 powdery mildews and gives the results of his investigations with Erysiphe graminis, 

 confining himself to forms of the fungus occurring on wheat and barley. In all mor- 

 phological characters the form occurring on the wheat is indistinguishable from that 

 occurring on the barley, but inoculation experiments showed distinctive physio- 

 logical differences. 



Inoculation experiments with the conidia of forms of E. graminis occurring on 

 a number of species of Bromus are reported, 1,650 inoculations having been made. 

 The results of the experiments show that a considerable number of the biological 

 forms exist within the genus Bromus, the fungus occurring on B. interrupts, B. 

 " hordeaceus," B. commutatus, etc., proving in each case to be a biological form pos- 

 sessing distinct infective powers. 



In addition to the high degree of specialization in the fungus it is also shown that 

 each species of Bromus has distinct physiological characters which exist along with 

 the specific morphological characters, and as a rule each species of Bromus possesses 

 characters which hold good for all examples of that species, no difference from what 

 source they are derived. A few species were found which indicate a complication 

 in the biological forms of the host plants. 



Investigations with the morphological species />. mollis show that there are at least 

 two distinct races of this species. 



In addition to biological forms of the fungus there were found to be certain species 

 of host plants which serve as " bridging" species. These seem to act as intermediate 

 hosts between other species, and inoculations from these give successful infections on 

 species otherwise resistant. 



In the second paper the author records the results of inoculation experiments 

 carried on with conidia of Erysiphe graminis from a number of species of grasses, of 

 Sphaerotheca hamuli on a number of host plants, and of E. cichoracearum, etc. The 

 result obtained showed that in every case the fungus studied had been specialized 

 into biological forms. 



