50 



INVESTIGATION INTO THE AMOUNT OF WAT EE 



perhaps with an apparently less succulent condition of the plant, 

 was in reality attained with any less degree of activity of the 

 fluids within it, or of watery exhalation from it, than during 

 the earlier stages of its growth. Upon this point some in- 

 formation will probably be afforded by our results as we proceed. 



The daily rate of evaporation in the cases of the two more 

 healthy clover plants — those, namely, of Series 1 and 2 — is seen 

 to be in the main higher up, to the time of their being cut, than 

 in those of the other plants ; in explanation of which it must be 

 remembered that the clover experimented upon, being the pro- 

 duce of seed sown in the previous season, these plants were, at the 

 commencement, more advanced than those with which they here 

 stand in comparison. 



The total evaporation from the jar without a plant is seen to 

 be 3844 grains during the entire period of the experiment. 

 This total loss from the whole of the glass lid is certainly con- 

 siderable, but it amounts on an average to little more than 3 

 per cent, of the entire quantity given off from the jars containing 

 the plants, and it seems unsafe on several grounds to attempt to 

 correct the indications of the latter by the deduction of the 

 amount of loss from the no-plant jar. Thus the loss from the 

 centre-hole of the no-plant jar might be supposed to exceed that 

 from the rest, since in these the orifice was nearly closed by the 

 stems of the plants : but, on the other hand, the much less active 

 circulation of air through the unplanted jar w ould tend to an 

 opposite result, as also would the fact, that in the absence of a 

 fresh supply of water in this case, the surface of the soil would, 

 after a time, become somewhat dry. That this was the case 

 would appear from the figures in the table, which show that 

 though the rate of loss from the no-plant jar increased for a 

 length of time as the season advanced, yet afterwards it to some 

 extent diminished. It may be remarked, however, that there 

 was frequently in this case, as well as in the others, a condensa- 

 tion of water on the under surface of the lid. Upon the whole, 

 then, we are inclined to decide that the indications of this ex- 

 periment should serve rather to prevent any too nice application 

 of the numerical results obtained in relation to the plants, than as 

 providing any available means of correcting them. 



Let us now turn our attention to the amount and composition 

 of the produce obtained from the experimental jars. The wheat 

 plants in all three of the jars appearing sickly from the time of 

 transplanting, were cut down twelve days afterwards, viz., on 

 March 31st, in the hope that they would then grow up more 

 vigorously. These cuttings, when dried at 212°, in neither case 

 weighed one grain, but they were saved, and their quantities are 

 taken into account with the rest of the produce. Stems 



