limits of their ranges as contrasted with 9eeds from the Qorthera 



limits. 



Most varieties of strawberries grown in the Northern States form 

 their flower buds during shorl days, bul they flown- and fruit during 

 the long days of early summer. If attempt- are made to grow most 

 of these northern varieties in the South, where daylighl period- are 

 shorter, they form weak rosettes but bloom very sparsely or not at all. 

 They produce little or no fruit. This is true despite the fact that 

 temperature and other environmental condition- are favorable. 

 Varieties adapted to the shorter day lengths occurring during the 

 winter months in Florida and other Southern States can be hied and 

 selected. The probability of their proving successful from the stand- 

 point of photoperiodic adjustment can be readily determined by first 

 growing them in a greenhouse where a photoperiod approximating 

 that prevailing in the South is created either by shading during day- 

 lighl hours of summer or by using supplementary artificial illumina- 

 tion in winter. If they do not flower and fruit under such experi- 

 mental conditions, they are not likely to prove successful out of doors 

 under the field conditions which the experimental condition- approxi- 

 mate. 



Selection of Varieties for Specific Photoperiods 



Soybeans are now widely grown in both the Northern and Southern 



States, with two principal objectives in view. One of these is the 

 production of seed- used in the making of oil, plastics, and several 

 food products. The other is the use of the whole plant for forage or 

 for tu rnin g hack into the soil in order to improve its texture and 

 fertility. Many varieties are grown. Bach has some particular 

 quality of special value. Some, especially the variety Biloxi, do not 



bloom unless the light period to which they ale exposed each day is 

 less than 1 .") hours. In the North, Biloxi ha- little value a- a crop and 

 does not bloom sufficiently early to mature seed- before frost. In the 

 Southern States, however, there is a sufficiently lon<r interval after l he 

 periods of daily illumination become short enough for flowering to 

 permit the seeds to mature. Other varieties develop flower- during 

 the long days of northern summers and mature abundant crop- of 

 >crd before killing frosts. The variety Agate will develop flower- 

 under continuous illumination, although it flowers more abundantly 

 if the light periods are shorter and it is exposed to a dark period each 

 day. 



The soybean well illustrate- a crop of which there are many well- 

 recognized varieties that -how a wide range of photoperiodic adapta- 

 tion. Whatever other desirable qualities a variety may have, if it is 

 to be grown lor seed production it is ncee— ar\ t hat it be adapted to the 

 photoperiodic conditions which prevail in the locality where n i- i<> he 

 grown. Failure to recognize tin- fact i- one of the factor- which limit 



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