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certain area of the more northern range of its cultivation the 

 sweet potato seldom blooms. In the tropics many, if not all, 

 varieties bloom and often in profusion. This behavior is, it 

 would seem, a response to environmental conditions, the most 

 important external factors being, without doubt, temperature, 

 length of growing season, length of day and intensity of light or 

 perhaps a combination of some of these. This is suggested by 

 the observations and results especially those of Professor Price 

 for Mississippi, Dr. Groth for Santo Domingo and Messrs. 

 James H. and W. R. Beattie of the U. S. Department of Agri- 

 culture. The effect of such environmental influences or the 

 formation of flowers has long been recognized (see numerous 

 earlier papers by Mobius, Vochting, Klebs, Sachs and Goebel 

 and the reports of more recent investigations by Setchell and by 

 Garner and Allard). 



Undoubtedly throughout the areas in which flowers appear 

 sparingly and irregularly there may be more or less blasting of 

 flower buds and some blasting of stamens only as indicated by 

 the reports for Mississippi. But for most varieties, if not for all 

 of them, the flowers seem to be perfect at least under conditions 

 of favorable development. The sterility does not seem to 

 Involve a relative impotence of either pistils or stamens as in 

 intersexes. 



But in areas where flowers are readily and abundantly pro- 

 duced, fruit and seeds are most frequently not to be found. 

 Several of the reports show that artificial self-pollinations have 

 failed to effect fruit setting. There are several of the reports 

 which indicate that when seed has been obtained there has usu- 

 ally been opportunity for cross- pollination. There appears to 

 be some type of sterility operating which limits self-fertilization 

 and which makes proper cross-pollination necessary for the 

 formation of fruit. The individual flowers are open for a rather 

 short time and the pistil and stamens in a flower seem to mature 

 at quite the same time. The conditions suggest that there is 

 functional or physiological incompatibility between the two 

 kinds of sex organs involved in the processes of fertilization — a 

 type of sterility very frequent In many hermaphrodite plants. 

 Further observations of the flowers, with studies of the pollen 

 and with tests by controlled self- and cross-pollinations are 

 needed to determine more exactly the type of sterility present 

 in the sweet potatoes. 



