742 EXPERIMENT STATION RECORD. 



effect of light, and of the relation of light to greenhouse culture, pathological 

 conditions, and greenhouse construction and management. 



All light records in these experiments were obtained by exposing tubes of a 

 uniform size and quality of glass filled with certain chemical solutions sensi- 

 tive to light. Tests were made of morning light v. afternoon light, different 

 qualities and kinds of glass, new v. old glass, the effects of different angles 

 of glass on the light in greenhouses, reflection of light from different surfaces, 

 loss of light from lapped glass and shadows, intensity of liglit at different 

 distances from the glass, loss of light from glass as compared with outdoor 

 light, and the rehitive value of different types of houses from the point of 

 view of light. 



In these experiments morning light was on an average 10 per cent more 

 intense than afternoon light. This dift'erence varies throughout the year and 

 from year to year. In some months it is as high as 30 per cent. In order 

 to take advantage of the more intense morning light, it is suggested that 

 houses which are usually placed east and west should be given a direction of 

 from 15 to 30° north of east. The additional light thus given the plants 

 will lessen the danger of infection from fungus diseases when it becomes 

 necessary to syringe the plants. Other influences being equal, a crop will 

 show a greater development on an east than on a west exposure. 



Considerable difference was found in the light-transmitting properties of 

 glass. Second quality, double thick, greenhouse glass transmits IS per cent 

 less than No. 1, double thick, and the third quality, double thick transmits 33 

 per cent less than No. 1, double thick. An irregular surface and defects, such 

 as bubbles, etc., in glass act as lenses and affect the even diffusion of light. 

 New glass proved to be slightly superior to used glass but the deterioration 

 from dirt and other factors is much less than 1 per cent per annum. In these 

 tests the practice of lapping glass caused an average loss of light of about 

 11 per cent. The loss of light from glass as compared with outdoor light 

 may vary from 13 to 36 per cent or more, depending on the quality and condition 

 of the glass and many other factors. 



It was found that transmission of light increases as the angle of the roof 

 more nearly coincides with the right angle of the sun's rays. The reflection 

 of light from surfaces varied greatly. In these experiments aluminum bronze 

 color constituted the best reflector of light. There appear to be no important 

 differences in the light in a greenhouse at different distances from the glass, 

 except immediately under the glass where the light varies in intensity owing 

 to the irregularity of the surface. Practically the same light is obtained at 

 5 ft. as at 30 ft. from the glass. Double glazed houses are much inferior as 

 to light transmission to single glazed houses. 



[Horticultural investig-ations in Alaska], C. C. Georgeson et al. (Alaska 

 &tas. Rpt. 1912, pp. 10-lS, 16-27, 55, 56, 66, 61, pJs. .J).— As a result of the 

 crosses between cultivated strawberries and the native berries of the coast 

 region (E. S. R., 28, p. 435), 334 out of more than 2,600 hybrid seedlings have 

 produced large to veiy large berries, and many others have yielded medium- 

 size berries equal to the average cultivated berry. The work of selection among 

 the best varieties will be continued. Crosses have also been made between 

 cultivated varieties and the species of interior Alaska with a view of securing 

 improved varieties which will prove to be hardier than the cultivated coast- 

 region hybrids. It is not expected that any of these strawberries will do well 

 south of latitude 49°. 



The following varieties of apples in the test orchard at Sitka set fruit in 

 1912: Tetofsky, Raspberry, Patten Greening, Oldenburg, Whitney, Hyslop, Pyriis 

 haccata, and the native crab. Of these, fruit matured only on the last 4 named. 



