AGRICULTURAL BOTANY. 127 



As a result of Lis studies it has been ascertained that the rate of formation 

 of carbon dioxid in the soil is directly proportional to the biological activity 

 of that soil.- It is also learned that temperature plays an important part in 

 deciding whether ammonification will proceed at such a rate as to allow con- 

 current nitrification. Some experiments were conducted which demonstrated 

 that where intense bacterial action is taking place in soil any nitrates present 

 may be reduced without the occurrence of anaerobic conditions, and it is 

 probable that the nitrate is utilized as a source of nitrogen by bacteria. In 

 another series of experiments it was determined that in puddled soil the 

 anaerobic conditions prevailing prevented the formation of nitrate, confirming 

 the conclusions of others that the rice plant obtains its nitrogen in the form 

 of ammonia and that the use of nitrate of soda as a rice fertilizer results in 

 a loss of nitrogen through denitriflcation. 



Some brief notes are givcni on a bacterial disease of tobacco due to Bacillus 

 solanaceanim, and a bacterial disease of wheat which was found to be 

 attacked by a bacillus closely resembling Pscudomonas hyacinthi. 



On the fungi of the soil, II, Elizabeth Dale (Ann. Mycol., 12 (1914), ^^o. 1, 

 pp. 83-62, pis. 5). — In continuance of previous work (E. S. R., 28, p. 524), the 

 author reports her studies on the fungus flora of three other samples of soil, 

 namely, chalk, uncultivated mountain peat, and black earth of reclaimed fen- 

 land. These gave respectively 29. 20, and 18 species, representing respectively 

 16, 13, and 13 genera, a few species and several genera being found in two or 

 more of the soils examined. None is known to be new. 



Bacteria and soil fertility, P. E. Brown (loica Sfrr. Cirr. 7 (19J3). pp. 16, 

 figs. 9). — This is a popular discussion of bacteria, and some of their functions 

 in soils are described. 



The mycorrhizas of forest trees, AY. B. ISIcDottgall (Amcr. Jour. Bot., 1 

 (1914), ^^0. 2, pp. 51-74, P^■'^'■ 4, fl'J- D- — This is a detailed account of a previous? 

 paper (E. S. R.. 30, p. 132). 



In the present report the author describes six forms of ectotrophic mycor- 

 rhizas and adds four species to hie known list of fungi which form ectotrophic 

 mycorrliiza.s. These are Russula sp., Boletus scaher fuscus, Cortinarius sp., 

 and Scleroderma vulgare. It is said that at least four and probably more spe- 

 cies of mushrooms may form mycorrhizas on the same tree. 



Infection for the formation of ectotrophic mycorrhizas is .said to take place 

 by a fungus penetrating the outer portion of the epidermal wall of the root and 

 then branching and spreading in all dii'ections. As soon as a complete mantle 

 of mycelium is formed over the root, any further length of growth is inhibited. 

 On this account the root is stimulated to form bi'anches which in turn are soon 

 infected. The fruiting bodies of an ectotrophic fungus are usually produced 

 soon after the mycorrhlza is formed. Both ectotrophic and endotrophic mycor- 

 rhizas are normally annual. They are formed during the summer, reach their 

 fullest development late in the autumn, persist throughout the winter, and die 

 in the spring. 



The roots of maple are infecteii through root hairs in the production of endo- 

 trophic mycorrhizas. The mycorrhizas of maples are said to be sometimes in 

 symbiotic association and at other times the fungus can only be considered as 

 an internal parasite of the roots. The ectotrophic mycorrhizas, on the other 

 hand, are not in any sense symbiotic associations, but are considered as para- 

 sites on the roots of the trees. 



The relation of living chlorophyll to light, D. Iwanowski {Ber. Deut. Bot. 

 Oesell, 31 (1914), ^o. 10, pp. 600-612, fig. J ) .—Detailing studies carried out 

 by himself with foliage differing as to thickness, as to area Cas related to vol- 



