113 
stance. In agricultural crops the amounts of water are still larger, 
sometimes reaching 95 per cent of the whole weight. 
The amounts transpired by cereals, grasses, weeds, etc., are consid- 
erably larger than the preceding, as shown by the following table 
compiled from Wollny’s results: 
in- Water consump- 
Plant. Year. ning of a ssa acre = 
How: pen: Pounds. Inches. 
Vi Iai iSTO TEN) See Sa ee ee a ee 1879 | Apr. 20} Aug. 3 | 2,590,000 10 
D3 TENN i Se Se a A a eR W8i9y |e2==do 222 -=-do-_-| 25,720; 000 11 
IRB Dente Se Aaa hee Pee Be SOR oe ee een eee 1879) j=: -2do-:-|--..do___| 3,140,000: | 12 
ieyeyel COWKAr LS ee Sy Se eee eee eee ae 18%9) |-.=-do_- | Oct. 11] 3,070,000 12 
DEUITEMM OTIS, © Sete nen cae esa ee eee eee soe a ...--| 1880 |_...do___| Aug. 14 | 3,000,000 12 
COTES era ce 1880 |_...do_--| Sept.14 | 3,420,000 14 
IB Calis eae eee ee Sone os ee se SSIS. SHEE et OX 1880 |....do-_-| Sept. 10 | 3,140,000 | 12 
1exaye! GONG)? 2S B= aS a ee ae eee ee 1880 |_...do_-_| Oct. 11] 4,110,000 | 16 
The following table is given by Risler (1873) in his * Note on the 
diminution of the volume of water courses,” and shows the mean daily 
consumption of water by plants, expressed in millimeters of depth 
of water over the area of the field: 
Daily con- | Daily con- 
Plant. sumption of |) Plant. sumption of 
water. water. 
mm. | | mm. 
ihucernoerass! 2.7.2 020-2. 22255.- Sade oe (eOul |« Clover see Benc tose see ese es eee 2.9 
THI OIT ASS —— ees ss ee oe 6 Fad Bey (a3 A 0 a ec Se EN ar 2.3 
(CANES! poe Sia nae eee esate ees ae Pepe Wawgeesy: 130 al SS rb d= ee oe en aS eee ees a ee ee UE ee eed len) 
IBBANSE toa ee StS oe Sipe eo eee 3.0+ POLATOCS tp ee es een eee ee Ontee at 
ENV ATs See Ore oe ie eee ee 2S 524. Onl | PING LOLOS bes se cae a ae a sae eee le) Ofb sare 
Wali Ga beeen sae fae.” ime DES ON ses Sall Oalkf OLesbscce onan eee ene- aoe wel ee O25 0X3 
These numbers have been deduced from the results of many years of 
experiments in the laboratory and from observations made in a 
drained field under conditions favorable to this kind of research. 
The crops have necessarily varied from one year to another, but 
unfortunately I am not acquainted with these details. 
The transpiration of the plant is only a means to an end. (See 
Marié-Davy, 1875, p. 209.) Its object is the introduction into the 
vegetable organism of the mineral elements necessary for the develop- 
ment of its tissues and that of the other principles united there. 
The experiments of Woodward and those of Lawes have already 
shown us that the same quantity of water is not always necessary 
in order to furnish the same amount of mineral substance and to 
produce in the plant all the elaboration and movements of organic 
products which should be produced there. 
It appears evident that in soils more or less fertile and which con- 
2667—05 M 8 
