VEGETABLE STATICKS 73 



He cfoes on to measure the surface of the roots ^ and to 

 estimate the rate of absorption per area. The calculation is 

 of no value, since he did not know how small a part of the 

 roots is absorbent, nor how enormously the surface of that part 

 is increased by the presence of root-hairs. He goes on to 

 estimate the rate of the flow of water up the stem ; this would 

 be 34 cubic inches in 12 hours if the stem (which was one 

 square inch in section) were a hollow tube. He then allowed a 

 sunflower stem to wither and to become completely dry, and found 

 that it had lost f of its weight, and assuming that the \ of the 

 " solid parts " left was useless for the transmission of water he 

 increases his 34 by ^ and gives 45^^ cubic inches in 12 hours as 

 the rate. But the solid matter which he neglected contained 

 the vessels and he would have been nearer to the truth had he 

 corrected his figures on this basis. The simplest plan is to 

 compare his results with those obtained by Sachs ^ in allowing 

 plants to absorb solutions of lithium-salts. If the flow takes 

 place through conduits equivalent to a quarter of a square inch 

 in area, the fluid will rise in 12 hours to a height of 4 x 34 or 

 136 inches or in one hour to 28*3 cm.^ This is a result com- 

 parable to, though very much smaller than, Sachs' result with 

 the sunflower, viz. 63 cm. per hour. 



The data are however hardly worth treating in this manner. 

 But it is of historic interest to note that when Sachs was at work 

 on his PJlanzenphysiologie, published in 1865, he was compelled 

 to go back nearly 140 years to find any results with which he 

 could compare his own. 



We need not follow Hales into his comparison between the 

 " perspiration " of the sunflower and that of a man, nor into his 

 other transpiration experiments on the cabbage, vine, apple, etc. 

 But one or two points must be noted. He found* the " middle 

 rate of perspiration" of a sunflower in 12 hours of daylight to 

 be 20 ounces, and that of a " dry warm night " about 3 ounces ; 



^ He gives it as i5"8 square inches, the only instance I have come across of his 

 use of decimals. 



^ Arbeiteii, \\. p. 182. 



2 See Sachs' Pflanzenphys. 1865 {Fr. Trans. 1868), p. 257, where the above 

 correction is applied to Hales' work. 



'' Vegetable Staticks, p. 5. 



