11 



MORNING VERSUS AFTERNOON LIGHT. 



A close observer will notice the effect of even small variations 

 in the amount and intensity of light on plant development, a single 

 cloud passing over the sun producing some effect, and a few hours 

 of cloudiness considerable effect. 



We have for many years been observing atmospheric conditions 

 of morning and afternoon, and the difference in morning and after- 

 noon light ; and the results of observations on the growth of plants 

 in the greenhouse have led us to believe firmly in the superiority 

 of morning over afternoon light. In fact, one hour of morning 

 light is in our opinion worth practically two of afternoon light in 

 the short winter days; and while this may be somewhat of an ex- 

 aggeration, there is a difference demonstrable by actual measure- 

 ments. This difference may be more noticeable some months 

 than others, but the average morning light is without doubt su- 

 perior to afternoon. Certain factors other than morning light 

 superiority may play some part in the better development of the 

 plant in the morning, although there is no proof of this. 



Mr. Alexander Montgom,ery, of the Waban Rose Conserva- 

 tories, Natick, Mass., and a very skilled observer of plants, has 

 for years believed in the superiority of morning over afternoon 

 light, and many of the Waban range houses were purposely placed 

 14 to 22 degrees north of east instead of exactly east and west. 

 In this position the houses are tilted toward the sun, and the plants 

 receive the morning sun more directly, which makes it possible 

 to syringe thoroughly without the usual risk of infection from fungi. 



The writer has frequently asked experienced greenhouse mana- 

 gers which light they considered the better, — m.orning or after- 

 noon, and he finds that few have ever given any thought to the 

 matter. Neither do meteorologists seem to have considered the 

 subject, and even photographers vary in their ideas as to the best 

 time of day for their work. But for many years we have had a 

 strong intuitive feeling that morning light is better, and therefore 

 determined to test them out. For two years before it was possible 

 to make an extensive study of this problem our assistant, Mr. 

 Monahan, helped devise many types of sensitive light recorders, 

 but all had to be discarded. By means of delicate galvanometers 

 and self-recording instruments, however, tracings showing varia- 

 tions in the intensity of light were obtained, but the chemical 

 method proved much superior, and all the records have been ob- 

 tained in this way. . 



The records of observations found tabulated in this chapter 

 were made during a period of one year, and while we have since 

 made many others in connection with other lines «f work, we have 

 not thought it necessary to give them here. 



