ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 221 



mycelium dies and moisture again penetrates the soil. The succession 

 of vegetation on the bare area is then (1) an earlj-weed stage, (2) a late- 

 weed stage, (3) a short-lived grass stage, (4) a perennial stage, which in 

 time gives way to (5), the original short-grass cover. A copious biblio- 

 graphy is appended. 



Climatic Conditions and Conidial Development.* — Y. W. Pool and 

 M. B. McKay have carried out a research on this subject, with special 

 reference to the wintering of Cercospora veticola, the fungus of sugar- 

 beet leaves. Dnring the winter the conidia remained viable for about 

 eight months in dry conditions ; in a moist atmosphere they died in from 

 one to four months. Humidity is of much more influence than tem- 

 perature on the development, and conidia are therefore more abundant 

 on the lower surface of the leaves, but also partly because they are 

 washed off the upper surface by rain. 



Effects of Pasteurization on Mould-spores, f — C. H. Thom and 

 S. H. Ayers have directed their attention to the success attained in 

 .destroying spores of fungi in milk by various stages of heating. The 

 different processes are described, with the results obtained. The " holder 

 process," in which milk is heated to 14.5° F. for a duration of thirty 

 minutes, killed the conidia of every species investigated except those of 

 Aspergillus repens, A. /favus, and A. fiimigatus, and these occur very 

 rarely in milk. After the "flash process" (165" F. for thirty seconds) 

 very few mould-spores survived. Oidkmi lactis and Mucors are killed 

 by the low temperature of the former process. 



Relation of Fungi to Host. | — Neil E. Stevens has published the 

 results of an investigation as to the effects of Botrytis on strawberries, as 

 compared with that of Rhizopus. With the former the mycelium invades 

 the cells of every part of the fruit, filling them up and producing some- 

 what of a mummified condition. The Rkizopus liyphai grew between 

 the cells, chiefly in the outer portions of the berry, separating them and 

 ■apparently extracting the cell-sap, but if grown on berries in a dry 

 atmosphere the mycelium penetrates to the centre of the berry, and 

 hyphge are frequently found inside cells. The berries attacked by 

 Rkizopus are soft and easily flattened. Stevens cites from literature a 

 parallel case where a Mucor reduced the pulp of a tomato to a fluid-mass, 

 the mycelium in this case also growing between the cells, while Fusarium, 

 which penetrated the cells, produced a dry-rot. 



Effect of Black-rot Fungus on the Apple. § — C. W. Culpepper, 

 J. S. Caldwell, and A. C, Foster record results of their investigation as 

 to the effect produced by Sphseropsis malorwn on the tissues and cell- 

 contents of the apple. The fungus attacks branches, twigs, leaves and 

 fruit ; their attention was restricted to the fruit. The loss of water, 

 they found, was small, but there was a very considerable reduction of 



* Journ. Agric. Research, vi. (1916) pp. 21-60 (2 pis. and 10 figs.), 

 t Journ. Agric. Research, vi. (1916) pp. 153-66 (3 figs.). 

 X Journ. Agric. Research, vi. (1916) pp. 361-6 (2 pis.). 

 § Journ. Agric. Research, vii. (1916) pp. 17-40. 



