AGRICULTURAL BOTANY. 825 



light absorption and tlie production of coloring raatprials in leaves, the author 

 states that the absorption of blue light waves is related to the presence of the 

 yellow pigment, which weakens greatly the violet rays which are energetically 

 absorbed by the photosynthetic pigments. These facts explain the protective 

 influence, previously noted, of the yellow pigments on the photosynthetically 

 active coloring material. 



The curve of absorption in clear .sunliglit shows a second maximum of 

 assimilative energy in the violet region, but its height is les.sened by the 

 presence of the yellow pigment. 



Gi-een plants are thus fitted by the properties of their pigments to assimilate 

 carbon in direct sunlight without suffering excessive injury to their chlo- 

 rophyll. They employ a portion of the energy of the less effective red rays 

 for this purpose, these being readily absorbed, while the violet rays are in 

 part suppressed by the yellow pigment. 



Substances separated by plants in arid reg'ions of Arg'entina, C. Spegazzini 

 (An. Soc. Cicnt. Arfjcntina, 77 (WU,), No. 5-//, pp. 15 1-1 58). —This is a di.s- 

 cussion of plant efflorescences, exudations, and incrustations under arid condi- 

 tions, as regards their production, properties, and probable significance. 



Chang'es due to climate and soil in cultivated crops, J. Bukovansky (Wiener 

 Landw. Ztg., 64 (1914), No. 93, pp. 823, 82^, figs. 2).— It was found that severe 

 losses in spring, despite promising early growth in case of clover from southern 

 Europe as compared with that from more northerly regions, were correlated 

 with the mode of gi'owth of the smaller roots, which in the former variety 

 radiated from a region near the surface, but in the latter branched mainly 

 from the deeper portions of a strong tap root. 



Phenological dates and meteorological data recorded by Thomas Mikesell 

 between 1873 and 1912 at Wauseon, Ohio, J. W. Smith (Mo. Weather Rev., 

 Sup. 2 (1915), pp. 23-93, pi. 1, fig. i ) .— Phenological data are given of 16 

 different Ivinds of fruits, 20 varieties of field and garden crops, 48 species of 

 forest trees, shrubs, and vines, and dates of blossoming of 114 different species 

 of plants, for the period 1SS3-1912. In addition, tables are given showing the 

 principal meteorological data and certain crop and fruit yields in the county 

 where the observations were made. No attempt has been made to correlate 

 the data regarding the weather conditions and the advance of vegetation, the 

 object of the paper being to record this new series of observations for the use 

 of students of the subject. 



Studies in the physiology of germination, E. Heilpekn (Osterr. Bat. Ztschr., 

 64 (1914), No. 7, pp. 286-293, figs. 2). — In experiments with seeds of /Ethusa 

 cynapium, Acer platanoifles. Geranium pyrenaieum. Ranunculus acer, (Enothera 

 biennis, and Silene acaulis, all showing a rest period, it was found that no con- 

 siderable influence was exerted on germination by exposure to snow, ice, water, 

 or air at 0° C. regardless of the existence of a rest period. 



As to duration, the rest period differed in different plants, appearing to be 

 in some degree an individual property, but not to depend upon locality and 

 date of harvesting in' a given .species. 



Dimorphism as to fruit forms was shown by Tragopogon dubius, T. orientalis, 

 and T. porrifolius, those of the first named showing also physiological dimor- 

 phism as regards germination. 



The action of plant metabolism products on plants, I, II, W. Sigmund 

 (Biochem. Ztschr., 62 (19W, No. 5-6, pp. 299-386; ohs. in Jovr. Chem. Soc. 

 \London], 106 (1914), No. 620, I, pp. 787-789).— These two articles deal with 

 the action of about 70 nitrogenous products on the germination of various seeds, 

 the first part dealing with alkaloids and the second including glucosids, tannins, 



