46 BULLETIN 428, U. S. DEPARTMENT OF AGRICULTURE. 
neath the surface of the soil and in certain cases to produce true pro- 
liferating lateral roots, and its ability to suspend activity and to 
lessen transpiration by reducing its leaf surface. During periods of 
severe drought it makes very little growth above ground, but appar- 
ently devotes some energy to the production of rhizomes, from which 
new growth develops either with the resumption of favorable condi- 
tions the same season or in the following spring. This adaptation is 
of considerable benefit in carrying plants through the critical periods 
of summer. 
The following heretofore unpublished data on the water require- 
ment of Medicago falcata, by which is meant the quantity of water 
required by the species to produce a given amount of dry matter, as 
determined by the method of Briggs and Shantz, have been fur- 
nished by Mr. A. C. Dillman, of the Office of Alkali and Drought 
Resistant Plant Investigations. 
A summary of the water requirement of Medicago falcata as compared with 
that of Medicago sativa (the Grimm variety), as determined at Newell, S. 
Dak., for four seasons, 1912 to 1915, inclusive, and at Akron, Colo., in 1914, is 
given in the following table: = 
TABLE VI.—Comparative water requirement of Medicago falcata and Medicago 
sativa at Newell, S. Dak., in 1912 to 1915, inclusive, and at Akron, Colo., in 
ADTS: 
Water requirement based on dry matter. 
Actual. Relative. 
Place, year, and species. 
First | Second | Third |Combined] First |Second| Third | COM 
crop. crop. crop. crops. crop. | crop. | Crop. | @& ops 
At NEWELL, S. DAK. 
Season of 1912:1 
Medicago faleata..........| 622415 | 735418 |--..--.-.. 663 +12 89 Ob ules 90 
Medicago sativa.......... 699+15 | 772+18 |.-...-.--- 735415 100 100) Sates 100 
Season of 1913: 
Medicago faleata......... 340+ 7 | 713411 |1,220452 | 579412 73 7 109 79 
Medicago sativa...-...... 469+ 6 817413 |1,115+16 735+ 8 100 100 100 100 
Season of 1914: 2 
Medicago faleata......... | §03+38 9303E 269s saaecee | 687 + 20 93 LIGS See 103 
Medicago sativa.....--... | 539 SOO ec Sees | 669 100 100:|22eeeeee 100 
Season of 1915: | 
Medicago faleata......... | 3994+ 8 | 4244 4 1,108+20 | 541+ 9 94 103 176 108 
Medicago sativa....--..-.- | 4244+ 9] 4134 7]! 630418 | 499+ 7 100 100 100 100 
Mean at Newell: 
Medicare ofaleataceecsss|bs esc soso | Pacem shel oeerecincs |maaeeeriee 87 100 142 95 
Medicacoisativiasc sass 2a s|et stoke) tere Severe esl eres alread tee ee ke res 100 100 100 100 
At AKRON, COLo. 
Season of 1914: ! 
Medicago faleata...-..---- 652+16 757413 |1,2014+75 | 848427 107 84 114 95 
Medicago sativa......-.-.- 610+ 3 907+14 |1,0554+12 | 890+ 6 100 100 100 100 
Mean at both Newell and 
Akron: 
Medicarofalcatascsaiaso: | tacsaee Here|ee ee a ecoe bemeaorreeral terse errs 91 97 133 95 
Niedicacoisativac sete ssl eee eben aces | a eee | Dia). saan 100 100 100 100 
1 The data at Newell, S. Dak., in 1912, and at Akron, Colo., in 1914, were procured from seedling plants, 
while those obtained at Newell in 1913 to 1915, inclusive, were from plants a year or more old. __ : 
2 At Newell, S. Dak., in 1914 there were five pots of Medicago falcata, but only one pot of Medicago sativa, 
