The Woburn Pot-Culture Experiments , 1913. 421 
any effect in the case of the lighter dressing, but with the 
heavier a distinctly toxic effect was produced. The heating of 
the soil, moreover, did not in any way get rid of the poisonous 
influence of the lithium salt. The appearances presented in 
these latter cases were most striking. It seemed as if on the 
heated soil a tremendous growth was first obtained, the plants 
throwing out fresh leaves, only to be destroyed, or partly so, by 
the toxic influence of the lithium ; a new growth was then 
sent out, and this, in turn, arrested, the general result being 
that the plants were never really able to produce fruit properly. 
With magnesia the results were somewhat similar, especially 
with the heavier application, but not so marked. It would 
seem that there was no great change so long as the lime 
remained in good excess, but when the addition of magnesia 
increased the amount to about that of the lime present, much 
the same results were found as have been noted previously in 
the case of wheat. 
Ultimately the fruit was gathered from each pot, and the 
comparative results are set out in Table IV. Plate 9 gives the 
appearance of the pots to which lithium phosphate had been 
added, and Plate 10 those where magnesia was the addition. 
Table IY . — Lithium Phosphate and Magnesia on 
Tomatoes , 1913. 
Comparative weights of fruit produced. 
59 99 
55 99 
95 55 
99 55 
95 
Normal Soil ..••••• 
with '0025 per cent. Lithium . 
„ '005 
containing '792 „ Magnesia 
„ 1-188 
„ „ „ 1-684 
Heated Soil ..*'•••• 
with -0025 per cent. Lithium . 
,, ‘005 ,, ,, 
containing -792 „ Magnesia 
1-188 
1-584 
5 5 
99 
55 
55 
5 *■ 
5 9 5 9 
59 *9 
55 9 5 
5 5 5 -> 
59 
95 
100 
29 
87 
89 
113 
12 
173 
71 
14 
131 
96 
22 
From these results it would appear that the toxic effects 
of both lithium phosphate and magnesia are more decided 
with tomatoes than with wheat. In no case has there been 
anything like the increase in crop which mere heating of the 
soil has effected. 
A remarkable feature in the addition of magnesia is that 
there was so little advantage from using heated soil as com- 
pared with the normal soil. A small side experiment was 
simultaneously conducted with magnesium carbonate in place 
of magnesia in order to see whether causticity might not be 
the reason of this, but it was found that the carbonate acted 
practically in like way : as the oxide. 
