TORREYA ::tV.^-- 



August, 191 1 

 Vol. II No. 8 



SEED WEIGHT IN STAPHYLEA AND CLADRASTIS 



By J. Arthur Harris 



In an interesting paper on light and heavy seeds in cereals Wal- 

 dron* concludes that in oats, plants with shorter culms, shorter 

 heads, and a smaller number of grains per head bear on the whole 

 grains of greater weight. Waldron's interest in the problem 

 was that of the plant breeder, concerned in determining the 

 results of selecting large or small seeds for planting, but they seem 

 suggestive for the physiologist as well. 



The explanation which the physiologist would at once suggest is 

 that the competition of an abnormally large number of seeds for 

 the available plastic material has, as a necessary result, a limita- 

 tion of the size of the individual seeds. While this seems a very 

 reasonable interpretation, one who has had experience in the 

 actual study of such phenomena will hesitate in accepting it 

 without further evidence. The discrimination and measurement 

 of the individual factors underlying such functions as fertility 

 and seed weight is an exceedingly difficult problem. As an 

 example, take the following case. If the seeds are smaller in 

 the larger inflorescences of Waldron's cereals because of the 

 finer partition of the available plastic material, one would 

 a priori expect that there would generally be a negative corre- 

 lation between the number of fruits per inflorescence and the 

 number of seeds which these fruits produce. So far as obser- 

 vations are available this is not the case. 



For a series of the climbing bitter sweet, Celastrus scandens,] 

 the correlations are: 



* Waldron, L. R. A Suggestion regarding Heavy and Light Seed Grain. Amer. 

 Nat. 44: 48-56. iQio. 



tAnn. Rept. Mo. Bot. Gard. 20: 116-122. 1909. 

 [No. 7, Vol. II, of ToRREYA, Comprising pp. 145-164, was issued 19 July 1911.] 



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