502 University of Calif omia Publications in Agricultural Sciences [Vol. 1 



range of concentrations emploj'ed in tlie copper series, there was 

 no pot receiving CuSO^ in am- qviantity which did not produce 

 more tillers than any of the control pots, which showed from 

 thirteen to fourteen tillers in each of three pots employed as 

 untreated controls. In general, therefore, it seems that in the 

 first crop, copper sulfate does stimulate tillering, but it does so 

 irregularly and small amounts of the salt appear to be as effect- 

 ive in that direction as large amounts. In the second crop of 

 the CuSO^ series the number of tillers was decreased throughout 

 because of climate and other obvious effects accompanying the 

 conditions of the experiment which are above described. Never- 

 theless, the treated pots were, with very few exceptions, decidedly 

 superior in tiller production to the untreated pots, which, again, 

 agreed well among themselves. Otherwise, the tillering of the 

 second crop in the CuSO^ series was not significantly different 

 from that of the first crop. 



In the first crop of the zinc sulfate series the number of 

 tillers was very markedly larger than in the first crop of the 

 copper sulfate series. Thus the largest number of tillers pro- 

 duced in the first crop of the copper series is about equivalent 

 to the smallest number of tillers in the first crop of the zinc 

 sulfate series. In one pot of the zinc series sixty-five tillers were 

 produced by four plants, a number more than twice as great as 

 the maximum in the first crop of the copper series. ^Moreover, 

 the agreement between duplicate pots was on the whole much 

 better in this regard in the zinc than in the copper series, despite 

 the fact that several large discrepancies were noted. In the first 

 crop, therefore, the zinc sulfate, like copper sulfate, has not 

 only stimulated tiller production, but has done so to a much 

 more marked degree than the last-named substance. In the 

 second crop, however, conditions and results are considerably 

 changed. Thus, whereas the stimulating effects of CuSO^ on 

 tiller production are clearly manifest throughout the series, 

 even after the salt concentration is doubled in the same soil, 

 only one case of stimulation in that respect (at the lowest con- 

 centration) is noted in the ZnSO^ series under similar conditions. 

 Moreover, in the CuSO^ series we find scarceh" one undoubted 

 case of depression in tillering even in the second crop, due to 



