Alfalfa Seed Yields 
29 
A contrast in seed setting ability on plants grown under exactly the same conditions. The 
plant at the right is heavily set with seed, that at the left almost devoid of seed. 
It was clearly evident that the cause for this good seed setting 
was entirely local. The elfect was limited to the branches that hung 
over into the ditch. The ditch was perfectly dry. It seemed evident 
that heat was the important influence peculiar to these branches 
in the ditch. The only two factors which were dilfermit for the 
branches out of the ditch and the branches in the ditch were heat 
and light. The free circulation of air Avould be somewhat obstructed 
by the bank and surrounding vegetation. The dry, sandy soil would 
reflect both heat and light. The air and branches in the ditch would 
become very warm during the heat of the day. This instance was 
the first practical evidence of the Effect of some one cause as a prime 
factor in prolific seed production which has occurred in the past 16 
years in which alfalfa seed production has been under investigation. 
The effect of this observation may not be easy to analyze. But 
it is evident that there is some physiological relationship between 
the effects of heat or heat and light and the efficient fertilization of 
alfalfa flowers, which is equivalent to saying that there must be 
some relationship of heat and light and the proper functioning of 
the processes of reproduction. It at least gives a clue for further 
investigations. Climatic conditions are evidently the most potent 
