28 



BULLETIN 75, V. S. DEPARTMENT OF AGRICULTUEE. 



Table XIX. — Weight {in grams) necessary to trip alfalfa flowers on different plants at 



different stages of maturity. 



At Alm.\, Nebr.i 



Planf. 



Young 

 flowers. 



Prime 

 flowers. 



Old 

 flowers. 



F. C. 1. 138 . 



2.14 

 3.89 

 6.42 

 3.37 

 7.12 



1.49 

 3.37 

 3.56 

 2.54 

 3.69 



68 



F. C. 1. 139 



3.37 



M.1221 



2.60 



M. 1222 



1.30 



F.C. I. 142 



2.14 







Average ." .^ 



5.18 



2.92 



2.07 







At Arlington Farm, Virginia. 2 



F.C.I. 99 



6.57 

 2.07 

 4.79 



2.22 

 1.49 

 3.04 



1.68 



S. P. I. 17992 



.33 



S. P. 1. 21232 . . . 



.45 







Average 



4.21 



2.33 



.77 







' Experiment performed August 4, 190S. Temperature 98° to 101° F.; humidity very low; bright sun. 

 Number of flowers used in experiment as follows: Young, 16; prime, 22; old, 21. 

 2 Experiment performed July 2, 1908; used one flower at each stage of maturity. 



Observations made at different times and places indicate that 

 wind or rain do not ordinarily cause alfalfa flowers to become tripped. 

 Even when blowing with high velocity the wind sways the plants 

 back and forth usually without causing the racemes to strike against 

 adjoining plants. At Chinook, Mont., during a high gale accom- 

 panied by a rainstorm, which lasted for a few minutes, a small pro- 

 portion of a number of flowers that had been marked was tripped. 

 The number of flowers which become tripped through the influence 

 of wind or rain, however, in ordinary seasons is evidently small, 



EFFECT OF PARTIAL SHADE. 



In conducting the experiments described in this paper it has been 

 observed that on the different plants used those flowers which have 

 been inclosed in the covering made by a single thickness of mosquito 

 bar remain in bloom longer and that the petals seem to be larger 

 than on those flowers which were not inclosed. As it seemed possible 

 that the effect of the slight shade or the breaking of the force of the 

 wind might also influence the development of pods and seed, an experi- 

 ment was performed at Pullman, Wash., in 1908, to obtain some infor- 

 mation in regard to this point. 



Several plants were selected, and a portion of each plant was 

 inclosed in a tent made of netting (tarlatan) ; the remaining portion 

 of each plant was not inclosed, but was protected on three sides and 

 partially from above by one thickness of netting, which was between 

 the plant and the sun and also between the plant and the prevailing 

 winds, yet did not prevent the access of bees and other insects. 

 The results of this experiment are shown in Table XX, in which the 

 results secured on unprotected plants at the same time and place are 

 also pi'csented for the purpose of comparison. 



