62 BULLETIN OF THE BUSSEY INSTITUTION. 
In comparing the results of these trials with those obtained in 
Series C, it is to be observed that the plants in Series D (planted 
January 11) were exposed, not only to more daylight than those plant- 
ed a month earlier, but, as it happened, to much more sunlight. 
Their life was more vigorous than that of the plants in Series C. 
Owing to the inevitable variations of the seasons, it is important that 
experiments of this sort should be made side by side, in order that 
the results obtained may be, strictly comparable. 
The nitrogenized solutions employed in Series D were stronger 
than those used in the preceding series, excepting only the solution 
of nitrate of lime. Due allowance must be made in several instances 
where one or more of the seeds planted failed to grow. As has been 
stated already, the coal-ashes of Series D were obtained from a differ- 
ent furnace from the one that supplied the ashes of Series A and B, 
and from another lot of coal. It is plain from the results tabulated 
above, as it was from the appearance of the plants during their 
growth, that the ashes of Series D contained, or in some way sup- 
plied to the plants, a small proportion of nitrogen.* So good a crop 
was obtained from these ashes by the use of rain-water alone, as 
well as by the use of rain-water containing matters which had been 
found by the experiments of Series A, B, and C to be useless in the 
absence of nitrogen, that the best crops in this set of ash experiments 
seem small by comparison. Yet the absolute weight of the crop watered 
with nitrate of lime, for instance, is greater in Series D than in Series B. 
* Tam at present unable to explain the occurrence of nitrogen in this connec- 
tion. No compound of cyanogen, of ammonium, or of nitric acid could be detected 
in the ashes. The rain-water of course contained the trace of nitrate of ammonia 
proper to it. But how little importance is to be attached to that source of nitrogen 
may be seen by inspecting the results of the experiments upon pit-sand and Berk- 
shire sand as well as the previous set of experiments (Series B) with ashes. It is 
conceivable, perhaps, though hardly probable, that the nitrogen of torrefied anthra- 
cite, like that of roasted leather, may be available for plants. The matter needs 
investigation. 
