532 University of California Puhlications in Agricultural Sciences [Vol. 1 



kind, from that of the corresponding oiie in the MnSO^ series. 

 Respecting root yields, the toxic effects of MnCl, in the second 

 crop are apparent throughout the whole series. While the de- 

 creases are not quite so great at the lower concentrations of 

 MnCL as they are at the higher concentrations, they are not 

 far different, and in general amount to from 40 to 60 per cent 

 of the amount yielded by the control pots. We see in the root 

 yields, therefore, a further analogy between the second crop of 

 the MnClo series and that of the MnSO^ series. In brief, it 

 should be observed that while wide discrepancies in total yields 

 of dry matter are noted between the second crops of the MnCl, 

 and MnSO^ series, the discrepancies are superseded by striking 

 resemblances when the straw, grain, and root yields are com- 

 pared separately in the two series. Since the differences seem 

 to be those of degree only, is it not possible that we have here 

 the dominant manifestations of the effects of manganese, which 

 are o\\\j slightly modified b,y the element or elements combined 

 therewith? If this were not the case, would we not expect to 

 find much larger discrepancies between the two series in ques- 

 tion, based on the specifically different effects of the -CI and 

 the -SO4 ions on barley growth ? 



Third Crop 

 The stimulating powers of manganese, as exemplified in the 

 effects of MnS04 ions on the third crop of barley, are again 

 manifest but very much more strikingly in the third crop of 

 the MnClo series. While the yields of duplicate pots still fail 

 to agree closely in a number of the salt concentrations tested, 

 they show a much better agreement than those of the MnSO^ 

 series. At any rate, there can be no doubt of the stimulating 

 effects of manganese chloride for barley grown in tlie greenhouse 

 soil even in the third crop. Again, as was the case in the MnS04 

 series, the ]\InCL, stimulates the production of all parts of 

 the plant and not merely of any one portion of the dry mat- 

 ter tht^reof. Thus, for example, whereas there was practically 

 no stimulation to grain production in the second crop of the 

 MnClo series, the third crop shows such stimulation markedly 

 throughout the series. In no case, further, so far as the total 



