24 



INTENSITY OF LIGHT AT DIFFERENT DISTANCES FROM 



THE GLASS. 



For many years there have been conflicting opinions in regard 

 to the light in greenhouses. An old idea which has been handed 

 down from, generation to generation and which has even been 

 taught in some of our institutions is to the effect that it makes 

 considerable difference in its growth whether a plant is near the 

 glass or some distance from it, the light being thought to be m,ore 

 intense near the glass. It has been stated that even lettuce and 

 cucumbers must be near the glass for the best growth. 



Modern greenhouse construction, however, has in the main 

 followed lines quite the reverse, the larger houses meaning a greater 

 distance between the glass and the plants. 



The author of an article in the "Gardeners' Chronicle", Lon- 

 don, quoted in "Horticulture",* regrets the modern tendency to- 

 wards large houses. He mentions the difficulty of getting plants 

 started where they are so far rem.oved from, the glass, and also 

 calls attention to independent circuits of air and the susceptibility 

 of plants to attacks from green fly, m.ildews, etc. Mr. Alexander 

 Montgomery, Jr., who was making light tests in his houses when 

 this article appeared, comments on the article in "Horticulture" 

 as follows: 



"The question of large versus small houses, as it presents itself 

 to us, is one which will have to be settled in the dear school of 

 experience. The subject has of course two separate phases; first, 

 the cost of construction and maintenance of large as compared 

 with small houses, and second, the question as to which is capable 

 of producing the higher grade of flowers. The first, we believe, is 

 generally conceded in favor of large houses by those who have con- 

 sidered the matter at all. The second is evidently the point which 

 is giving the critic in the above notes some cause for worriment. 



His complaints resolve themselves into two divisions; danger- 

 ous draughts owing to extreme length and width, and lack of light 

 on account of the distance of the plants from the glass. If a house 

 40 feet wide and 700 feet long may be considered large, we can say, 

 as far as our experience goes, that the fears of our critic are not 

 well founded in either case. In this structure the temperature and 

 ventilation, both day and night, are under more perfect control 

 than in any other house on the place, and we are finnly convinced 

 that, in this respect at least, it is very much superior to the eight 

 small houses which it would require to cover the same am.ount ot 

 ground. 



The point in regard to light we think we have settled, for this 

 house at any rate. Ordinarily the test for this would be by close 

 observation of the plants at the varying distances from the glass. 



♦Horticulture, Vo. VIII, No. 12, March 21, 1908, p 304. See also Horticulture, Vol. 

 V. No. 10, March 'J, 1907. p. 286. 



