144 Journal of Agricultural Research voi. xm, no. 2 



bled in Table IV. The comparison of weather conditions at these two 

 points, both of which are in southern California, is available in Tables I 

 and II. 



It will be noted in Table IV that most of the data from Bard are for 

 the year 191 5, while those for Chula Vista are for 1916. The weather 

 conditions at Chula Vista and Bard are so uniform from year to year 

 that the comparison has practically the same value as if all the plantings 

 had been made in 191 5 at both places. The greatest factor of uncer- 

 tainty in the tabulated data is the effect of the date of planting. At 

 Bard in 191 5 most of the numbers were planted about the middle of 

 April, while in 191 6 the plantings were not made until the middle of 

 June. The effect which this early planting had on the sorghums is 

 brought out more fully in Table V. It can be said here, however, that 

 the later planted sorghums were more nearly normal, especially in the 

 seed parts. 



Table IV gives a comparison not only of the growing season anu 

 height, but also of the number, length, and width of the leaves, and the 

 length and diameter of the panicles. For the varieties which were planted 

 at both places in June the magnitude of all characters was greater at 

 Bard than at Chula Vista and the growing season was shorter. This 

 difference of 21 days in the growing season is perhaps a fair measure of 

 the effect of the low temperatures and reduced actinic value of the sun's 

 rays at Chula Vista. High fogs obscure the sun quite often for hours 

 in the morning and evening, and the temperature is seldom above 70° F. 

 for any considerable part of the day. At Bard, on the other hand, desert 

 conditions prevail, the sky is usually cloudless and the sunlight is intense, 

 while the temperatures reach a maximum of over 100° F. day after day. 

 Considering only the three varieties White African sorgo, Blackhull 

 kafir, and Brown kaoliang which were planted at Bard on June 14, 191 6, 

 and at Chula Vista only two weeks later, the sum total of the positive 

 temperatures received from planting date to maturity was at Bard 

 4,301° F. and at Chula Vista 1,923° F. It is evident, therefore, that 

 although the growing season averaged 28 days shorter at Bard there 

 was available for the plants' use a much larger number of heat units 

 than at Chula Vista. These conditions resulted in taller, slightly larger 

 stems, and a greater number of leaves which were both longer and wider, 

 except in the early planted sorghums at Bard which had slightly narrower, 

 though longer leaves than at Chula Vista. The panicle was larger at 

 Bard, especially in the sorghums which were planted at both places in 

 June. 



The most remarkable variation which took place, however, is in the 

 number of leaves, a character that has heretofore been considered rela- 

 tively stable. All the plantings were made with seed from bagged 

 heads, so the variation can not be attributed to cross-pollination. Dwarf 

 hegari, which exhibits an extreme variation of 12 leaves, is notoriously 



