1917] AGRICULTURAL BOTANY. 221 



potted soils at Madison, Wis., wliere tlie variations in temperature are said to 

 be greater tlian ttiose recorded by former investigators. The results are 

 reported to have shown a close relation between the moisture content and the 

 number of bacteria in the soil, also a distinct retardation caused by cold, 

 which even a higher moisture content was usually insufficient to counteract. 



Incubation studies with, soil fungi, S. A. Waksman and R. C. Cook {Soil 

 Sci., 1 (1916), No. 3, pp. 275-284, fid- i).— Describing studies with three fungi 

 in order to ascertain the ways in which the lengths of the life cycles of fungi 

 affect their relation to soil fertility, the author states that the optimum moisture 

 conditions for ammoniflcation by fungi lie near the physical optimum. While 

 each organism has its own incubation period, the employment of a 12-day period 

 is preferred as most suitable for practical work. The biological stage of the 

 fungus seems to show correlation with ammonia accumulation. The largest 

 amount appears during spore gex'mination, the smallest during the time pre- 

 paratory to actual spore formation. Monilia sitophila showed the largest 

 accumulation within the first 3 or 4 days, a Penicillium studied between 10 

 and 15 days, and Mucor plumbeus between 6 and 10 days, these periods corre- 

 sponding to those of active spore formation. 



The inoculation and incubation of soil fungi, N. Kopeloff (Soil Sci,, 1 

 (1916), No. 4, pp. 381-403, figs. 8).— The author, having made a study of the 

 accumulation of ammonia by Rhizopus nigricans, R. oryzce, Zijgorrhyncus vuil- 

 leminii, and Penicillium sp., states that an increase in the number of spores 

 used to inoculate the soil caused a proportional increase in ammonia accumula- 

 tion. One cc. of spore suspension is regarded as the most desirable quantity, 

 all factors considered, for inoculations in experiments with pure cultures of 

 soil fungi. To increase the number of inoculating spores beyond a certain 

 point does not further accentuate the difference between ammonification of 

 dried blood and that of cottonseed meal, the latter appearing to be a better 

 source of food for the organisms employed. 



With Z. vuilleviinii, the maximum ammonia accumulation occurred on the 

 twelfth day with both the above foods. R. nigricans gave its maximum with 

 dried blood on the seventh, and with cottonseed meal on the ninth, day. A 

 seven-day incubation period is regarded as the most advantageous, all factors 

 considered, for a study of soil fungi other than those of the Penicillium group. 

 After the first five days a striking increase of ammonia production is observed 

 to occur every other day. It is thought that ammonia production depends upon 

 the metabolic processes of the fungi rather than upon their biological stage. 



On pairs of species, R. R. Gates (Bot. Gaz., 61 (1916), No. 3, pp. 177-212, 

 figs. 12). — ^The author has begun a detailed study regarding the relationships 

 of particular species by an examination of pairs of species in the same genus 

 taken at random. It is considered as desirable that there should be developed 

 a taxonomy based on the anatomical and cytological study of plants. 



It has been found that the several pairs of species studied bear very different 

 relationships to each other, both as regards characters and distribution. They 

 may occupy identical, overlapping, adjacent, or widely separated areas. One 

 species may be a giant of another, or may differ from it by a few sharp differ- 

 ences which originated as units, or may show differences which can not be 

 externally analyzed in this way. Several such pairs are discussed with the 

 problems they present, as well as the agency of mutation (E. S. R., 34, p. 629). 



It is considered that crossing experiments and cytological investigations may 

 provide the final answer to the specific questions involved. 



Studies on the correlation of morphological and physiological characters: 

 The development of the primordial leaves in teratological bean seedlings, 



78786°— No. 3—17 3 



