for July, 1920 



263 



HEAT AND FRUITING 



It i> a mattiT of common 

 knowledge that plants must 

 have light to make plant food, 

 but according to two scientists 

 of the Bureau of Plant In- 

 du>try, U. S. Department of 

 Agriculture, the fruiting of 

 many, perhaps, all plants may 

 be controlled by regulating 

 the period of light to which 

 they are exposed. It is re- 

 ported that either too long or 

 too short a period of daylight 

 in comparison with the dark- 

 ness may prevent plants from 

 flowering or fruiting. In case 

 the period of light is unfavor- 

 able, the plants may make a 

 luxuriant growth, but fail to 

 fruit. A length of day that is 

 favorable to both vegetation 

 and fruiting is assumed to 

 produce the "'everbearing" 

 varieties. It has been known 

 for a long tiine that plants 

 have three cardinal tempera- 

 ture points or zeros — an 

 upper and lower zero beyond 

 which growth ceases and a 

 middle or optimum zero at 

 which they thrive best. Fre- 

 quently these zeros are dif- 

 ferent for the growing and 

 flowering processes. Undoubt- 

 edly the upper and low-er 

 zeros are associated with tem- 

 perature, but it may w-ell be 

 that the optimum point is 

 determined more by light. In 

 view of the experiments, one 

 understands how apple trees 

 may fail to fruit when taken 

 to a warmer region, not be- 

 cause of the heat, but because 

 the period of daylight is not 

 favorable. .A. curious result 

 of this rule is found in the 

 case of the ragweed, which 

 is reported to require for 

 flowering a stimulus that is 

 afforded by the shortenhig of 

 the days and Ivnjthening of 

 the nights. It docs net come 

 into flower until the period of 

 daylight falls below 15 hours. 

 In the latitude of Washing- 

 ton, that comes about July 1. 

 But if ragweed seed should 

 be taken to northern Maine 

 and planted, the plants would 

 not experience a length of day 

 below 15 hours until about 

 .August 1. Therefore, they 

 could not come into flower 

 until after .\ugust 1 and, 

 though the vegetative growth 

 might be very rank, they 

 could not mature seed before 

 killing frosts intervened. The 

 long days, therefore, make it 

 impossible for ragweed to 

 perpetuate itself in that lati- 

 tude. On the other hand, plants that get 

 their flowering stimulus from a long day 

 could not perpetuate themselves through 

 seed formation at the equator, where the 

 (lay never exceeds 12 hours. This principle 

 affords the clue to the fact that many plants 

 grow most luxuriantly near the northern 

 limit of their range. The long northern 

 day allows them to attain their maximum 

 growth before the shorter day intervenes 

 to check vegetative growth and start the 

 productive process. The migration of birds 

 is also said to be explained by this theory. 

 — American Botanist. 



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Boston 



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OlALITY RED POTS 



Made of best material by sklllH 

 lalxjT, luiifonnly burned and 

 carcfiiUy packed. 

 Famoos "Moss-Aztec" Ware 

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 and price list. 



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 So. Zanesvllk, Ohio 



ORCHIDS 



Wo nrc Spocinllsts in Urcbiils. We collect, 

 crow. Import, export and spII orchids ex- 

 clusively. If yoii lire In the market for Orchids, 

 wo solicit yniir Inquirira nmt orders. Cata- 

 logues and 8T>*'cinl lists on application. 

 LAGER & HURRELL 

 •rthid Growtrt and Importan 

 Summit, N. «J. 



*o^Sarborr>c 



The New Hardy Dwarf Edsiar and Low Hedn 



Oriuinatnrs awl Intr-'inctrs: 



The Elm City Nursery Company 



Woodmont Nurseries 

 Box 193 New Haven, Conn. 



and 



ud for Box-Barl)f rrv 

 General Nursery C^i 



talopn. 



