26 



Journal of Agricultural Research voi. xxii, No. i 



Table III. — Dry weight per plant of shoot, roots, atid nodules prodticed in 6j days in 

 the first series, grown in November, December, and January, and 55 days in the second 

 series, grown in April and May 



Temperature. 



°C 



12 



15 



18 



21 



24 



27 



30 



33 



36 



First series. 



Shoot. 



Gm. 



o- '^33 



. 410 



• 432 

 .632 



.875 

 .771 

 .818 

 .863 

 .996 



Root. Nodules. 



Gm. 

 O. 040 

 . IIO 



•135 

 . 140 



•131 

 .108 

 .096 

 .116 

 . 108 



Gm. 



O. 000 

 . 006 

 .008 

 •033 

 •043 

 .030 

 . 014 

 . 012 

 .005 



Second series. 



Shoot. 



Gm. 



0. 922 

 1.430 



1. 710 



1. 900 



2. 620 



2.540 

 2.440 

 2. 130 



Root. Nodules. 



Gm. 



3. 184 

 .318 

 . 269 

 . 296 

 •342 

 . 296 



•437 

 . 422 



Gm. 



O. 021 

 . 060 

 . 108 



•145 

 .094 

 .089 

 . 076 

 . 042 



/S /3 2/ 24 27 30 33 36 



Pig. 3. — Ratios ot weight of nodules to weight (A tops and of roots. First experiment. 



In order to obtain a clearer view of the contrast between the effect of 

 temperature upon weight of nodules and that of roots and shoots, the 

 ratios of the weights of these parts of the plant have been determined and 

 plotted (fig. 3, 4). If there is a direct relation between development of 

 nodules and that of either the aerial or subterranean parts of the plants — 

 if nodule development is conditioned by top or root development quite 

 independently of the temperature factor which was varied in these 

 experiments-^then the ratio should be approximately constant, or at 

 any rate should be a straight line. A glance at the graphs shows that 

 this is not the case. The ratios when plotted produce curves which are 

 closely similar. No direct relation appears to exist between weight of 

 nodules and that of either tops or roots under the conditions of these 

 experiments. At 21° and 24° C. the weight of nodules is relatively 

 larger than at temperatures above or below this region. The wide dif- 



