Bouyoucos, Transpiration of Wheat Seedlings as Affected etc. 7 



were carefully noted. It was observed that, as a general riüe, 

 the seedliug-s grown in the higher densities always made, at the 

 beginning, a much slower growth than those in the lowr concen- 

 trations. Indeed, it always appeared that the rate of growth 

 increased as the density decreased. After the first four or five 

 days, however, this order was reversed; the plants in the higher 

 densities began to grow very rapidly and the rate or mag-nitude 

 of growth became decidedly proportional to the concentration. 



In connection with the above Observation, it might also be 

 mentioned, that the germination of the seeds was also retarded 

 by the higher densities. The time required to sprout was propor- 

 tional to the concentration, and the difference in time between 

 the two extremes, was from one to two days. 



At the termination of each experiment a careful examination 

 was always made of the total growth and of the general appearance 

 of the plants, including both the tops and the roots, in all three 

 kinds of cultures. In the case of the tops, it was observed that 

 they were healthy, vigorous, and their total growth always tended 

 to increase with the increase in density. The roots also always 

 appeared to be healthy, vigorous and turgid, and their total weight 

 to be proportional to the actual weight of the tops. As to the 

 latter relation, several attempts were made to confirm it quanti- 

 tively by determining the dry weight of the roots and then com- 

 paring this with the dry weight of the tops. It was found, however, 

 that this comparison was not reliable, because the roots in the 

 different densities contained various amounts of fine sand particles 

 which were practically impossible to wash out. In view of this 

 difficulty, the determination of the dry w^eight of the roots had to 

 be abandoned, and therefore, the relation of the roots to tops, 

 roots to transpiration, and roots to density, all of which would 

 have been of great interest, could not be ascertained. 



The dry matter of the tops was determined by drying them 

 in a drying oven at the temperature of boiling water for about 

 10 hours and then after cooling, they were weighed on a chemical 

 balance. The total dry matter was then compared with the total 

 transpiration, and the amount of water required to produce one 

 gram of dry substance, calculated. 



Mention has already been made that this line of the research 

 involved five series of Solution cultures, nine series of sand cultures, 

 and four series of soll cultures. Inasmuch as all the different 

 series within the same culture received practically the same treat- 

 ment, and show almost the same order of results, it Warrants us 

 in arranging their individual' results, in averages. The main con- 

 clusions will, therefore, be drawn from these averages. These 

 data are given in the following tables. Each table is accompanied 

 by a diagram to illustrate its salient facts in a graphical form. 



It is evident from the foregoing talbes and diagrams that the 

 different densities of the complete. nutrient Solution have a very 

 significant effect upon the transpiration of the wheat seedlings, 

 and that this effect manifests itself in all three of the different 



