BOTANY. 325 



rust to distinguish it from the earlier form which attacks both black- 

 berries and raspberries, the late rust attacking only the blackberry. 



The tomato mildew (Gladosporium fulvum), a common disease in 

 greenhouses, is described, and the application of any of the ordinary 

 fungicides is recommended as a preventive treatment, together with 

 the precaution of burning all dead leaves and vines when the crop is 

 removed. 



A chrysanthemum rust is described, in which the form examined 

 closely resembled and probably is identical with Puccinia tanaceti, 

 which occurs on many of the composite plants. It is thought advisable 

 to spray the plants occasionally with Bordeaux mixture or potassium 

 sulphid solution, commencing early in the summer before the disease 

 appears. If plants are healthy when put into the house one or two 

 sprayings thereafter should carry them through the winter. 



" Drop " of lettuce, which is due to a species of Botrytis, is briefly 

 described, and numerous methods for controlling it are suggested. 

 What is considered the cheapest and probably the best method of 

 treatment, not only for this fungus but for other pests of the soil, is to 

 heat the earth with steam up to 130 to 200° P. While the author has 

 not tried this method, he supposes that if the soil was heated to 200° 

 F. it would result in the destruction of the fungus. 



Two physiological disorders of plants are mentioned — a wilt of inaple 

 leaves and top burn of lettuce. Both these diseases are intimately 

 connected with the transpiration and lighting of the plants. 



Experiments on the assimilation of ammoniacal and nitric 

 nitrogen by the higher plants, E. Laurent, E. Marchal, and E. 

 Oarpiaux (Bui. Acad. Roy. Set. Belgique, 1896, Dec. 12; abs. in 

 VEngrais, 12 (1897), No. 19, pp. 447, 448; Ann. Agron.,23 (1897), No. 

 5, pp. 235-237). — The authors have carried out an elaborate series of 

 experiments, the principal results of which may be summarized as 

 follows: 



The reduction of nitrates in green leaves is a phenomenon due prin- 

 cipally to the action of the more refrangible rays of the spectrum. 



In darkness the etiolated stems of the potato assimilate neither 

 ammoniacal nor nitric nitrogen. The green stems assimilate both 

 ammoniacal and nitric nitrogen in sunlight. 



The stems of asparagus, which contain little chlorophyll, assimilate 

 both nitric and ammoniacal nitrogen (the latter more rapidly than the 

 former) in sunlight. 



The blanched leaves of the elm assimilate nitric nitrogen with dif- 

 ficulty, perhaps not at all, and they appear to reduce nitrates with 

 difficulty. They, however, rapidly assimilate ammoniacal nitrogen. 

 In sunlight the green leaves rapidly assimilate both nitric and ammo- 

 niacal nitrogen, the latter more rapidly than the former. 



In sunlight the etiolated leaves of the ash-leaved maple assimilate 

 ammoniacal nitrogen much more rapidly than nitric nitrogen. Under 

 8563— No. 4 3 



