24 



BULLETIN 844, U. S. DEPARTMENT OF AGRICULTURE. 



immature pods. For this purpose several volunteer plants growing 

 in a meadow were selected. A hole 12 inches square and 14 inches 

 deep was dug 8 inches from the crown of one plant, and each evening 

 during the experiment 2 gallons of water were poured into the hole. 

 The top of the hole was kept covered, so as to check evaporation from 

 it as much as possible. Another plant of the same size and growing 

 about 15 yards from the watered plant served as a check. On both 

 plants many of the flowers and immature buds were aborting at the 

 beginning of the experiment. The soil in this field was so depleted 

 of moisture that the leaves of the plants wilted during the hottest 

 part of the days preceding the experiment. The foliage on the check 

 plant wilted each clay for the first five days of the experiment. On the 

 sixth day 0.96 of an inch of rain fell and four days later 0.23 of an 

 inch more. The dropping of the flowers was temporarily checked by 

 these precipitations, but owing to the dry, compact condition of the 

 soil the rain was not sufficient to check entirely the fall of flowers and 

 immature pods. At the beginning of the experiment the racemes on 

 both plants were divided into three classes, according to the develop- 

 ment of the flowers, and labeled. They were collected and the seeds 

 counted as soon as the pods at the bases of the racemes commenced 

 to turn brown. Table VIII presents the results obtained. 



Table VIII. 



-Effect of water upon the seed production of sweet clover when groiving 

 under droughty conditions at Ames, Iowa, in 1916. 



Stage of development when labeled- 



Flowers at the base of the racemes just ready to open. 



Pods 3 to 6 days old 



Pods 9 to 12 days old 



Plant not watered. 



Number 



of racemes 



labeled. 



Average 

 number of 

 pods per 



raceme 



that 

 matured. 



27.39 

 21.13 

 15.23 



Plant watered. 



Average 



Number feS 

 ofracemes,^^ 



that 

 matured. 



labeled. 



110 

 112 

 50 



55.63 

 39.81 

 29. S6 



Increase 

 from 



watering. 



28.24 

 18.68 

 14. 63 



The effect of the water was noticeable soon after the first appli- 

 cation, as the leaves and flowers on this plant became turgid and the 

 anther sacs burst at the proper stage of their development. Very 

 few flowers fell after the second day. The water decidedly checked 

 the aborting of immature pods, as is shown by the results obtained 

 on the racemes which were labeled after the pods had formed. The 

 racemes which contained pods 3 to 6 days old when labeled matured 

 9.95 pods to the raceme more than those which contained older pods 

 at the beginning of the experiment, but this was expected, as most 

 of the aborting which caused this difference had taken place before 

 the racemes were labeled. As very few pods aborted before they 

 were 3 to 6 days old, the difference of 9.95 pods to the raceme in favor 



