724 EXPEEIMENT STATION RECORD. 



kinds of cloth screeus of the light requiremeuts of plants with special reference 

 to their optimum at different stages of development, about a dozen species, rep- 

 resenting a number of the more common botanical orders, being investigated. 

 The influence of light on water content, fresh and dry weight, photosynthesis, 

 germination, vegetative growth, flowering, fruiting, and ripening have been 

 studied experimentally. 



In concluding his observations the author states that strong light in general 

 induces the accumulation of elaborated materials in the storage parts of plants, 

 such as rhizomes, tubers, fruits, etc., while more diffused light tends to the 

 utilization of the nutritive materials and as a consequence increases the growth 

 of such organs as leaves, herbaceous stems, etc. 



Observations on the connection between leaf form and light requirement, 

 J. WiESNER (Sitzher. K. Akad. Wiss. [Vienna], Math. Natunv. A7., 117 {1908), 

 I, No. 9-10, pp. 1251-121. 'i, fig. 1). — The author claims that extensive foliage 

 division, such as small or strongly dissected leaves resulting in small-volumed 

 assimilatory organs, is associated with a high light requirement minimum. 



"With trees and a large number of other plants w'hich shade a part of their 

 own foliage, the higher the minimum of light requirement the smaller the leaf 

 volume. This small leaf volume usually appears as needle or threadlike foliage, 

 of which the conifers are fine examples. Such finely divided foliage not only 

 secures for the plant the admission of an abundance of diffused light but also 

 secures an advantageous modification of the intensity of the direct rays. On 

 account of the small diameter and large surface of such leaves compared to 

 their volume their heating capacity is low, which is the more advantageous the 

 higher the light requirement. 



On the changes produced in direct sunlight when it enters the foliage of 

 trees and other plants, J. ^yIEsxER (Sit::ber. K. Akad. Wiss. [Vienna], Math. 

 Nat uric. KI., 118 (1909), I, ^o. 6, pp. 759-812, figs. 11).— The author gives the 

 results of investigations on the penetration of direct sunlight and of diffused 

 daylight into the foliage of plants through the small spaces between the leaves, 

 the change of intensity, and the transformation of direct sunlight into diffused 

 light within the foliage and tissues of the plants, and on the formation, size, 

 shape, and heat intensity of the sun disks or images formed on the ground in 

 the shade of trees. 



Perception of light by plants, A. H. Blaauw (Rec. Trav. Bot. N^erland., 5 

 (1909), No. 2-4, pp. 209-377, pis. 2, figs. 6). —The author critically reviews the 

 literature of light perception by plants and describes his experiments with 

 oats and Phycomyces nitens to determine their phototroinc reaction. The phe- 

 nomena attending such reactions are said to be due to three factors, the pri- 

 mary reaction which light directly exerts upon plants, the counter-reaction, and 

 the power of adaptation to the controlling light influence. 



The relation of hairy and cutinized coverings to transpiration, K. M. 

 WiEGAND (Bot. Gas., J,9 (1910), No. 6, pp. -',30-',',.',, fig. i).— This is a detailed 

 account of investigations noted elsewhere (E. S. R., 23, p. 130). 



Leaf color and chloroplastid formation in evergreen woody plants, V. Vouk 

 (Sitzhci: K. Akad. Wiss. [Vienna], Math. Natiira: KI., 117 (1908), I. No. 9-10, 

 pp. 1337-1378, figs. 6). — It is claimed that the deep green color of the mature 

 leaves of evergreens is due to several factors, of which the most important are 

 the increase in number and size of the chloroplastids followed by an increased 

 chlorophyll production, in which a decrease of xanthophyll in proportion to the 

 chlorophyll present occurs. 



The direct absorption of nitrites by plants, F. Perciabosco and V. Rosso 

 (Staz. Sper. Agr. Ital., .',2 (1909), No. 1-2, pp. 5-36, fig. i).— In a series of 

 experiments with different nutritive media il was found that wli(>n soiMllings 



