This work on transpiration involved a study of the competition and the comparison of the growth of wheat, of wheat with mustard, of oats alone and oats with mustard. To determine the growth and development taking place in the various cultures, measurements were made at frequent intervals of the increases in leaf area and of the amount of water lost. The data clearly show that weeds require a large amount of water.

Comparing the pure and mixed cultures leaves no doubt but that a weed like mustard impairs the crop. The effect is evidenced in the fact that a culture of wheat and mustard attained its maximum leaf area later than a culture which contained only wheat; cultures of oats and mustard attained maximum leaf area later than cultures of oats alone. The results secured indicate that such a procedure will cut down the dry weight produced.

It is brought out that where oats are grown thick enough, they will offer a competition between themselves. Such growth, however, offers better means for the eradication of weeds like mustard by the process of competition. From the results presented in this work, oats in all probability would be better for this purpose than wheat.