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Cuar. VIL] CARBONATE OF AMMONIA. 115 
leaf after immersion in a few drops of a solution of one grain of 
phosphate of ammonia to 200 oz. of water (ùe. one part to 87,500) is 
here reproduced: such energetic inflection is never caused by water 
alone. With leaves in the weak solutions, the blade or lamina otten 
becomes inflected; and this is so rare a circumstance with leaves in 
water that I have seen only two instances; and in both of these the 
inflection was very feeble. Again, with leaves in the weak solutions 
the inflection of the tentacles and blade often goes on steadily, though 
slowly, increasing during many hours; and this again is so rare a cir- 
cumstance with leaves in water that I have seen only three instances 
of any such increase after the first 8 to 12 hrs.; and in these three 
instances the two outer rows of tentacles were not at all affected. 
Hence there is sometimes a much greater difference between the leaves 
in water and in the weak solutions, after from 8 hrs. to 24 hrs., than 
there was within the first 3 hrs.; though as a general rule it is best 
to trust to the difference observed within the shorter time. 
With respect to the period of the re-expansion of the leaves, when 
left immersed either in water or in the weak solutions, nothing could 
be more variable. In both cases the exterior tentacles not rarely 
begin to re-expand, after an interval of only from 6 to 8 hrs.; that is 
just about the time when the short tentacles round the borders of the 
disc become inflected. On the other hand the tentacles sometimes 
remain inflected for a whole day or even two days; but as a general 
rule they remain inflected for a longer period in very weak solutions 
than in water. In solutions which are not extremely weak, they never 
re-expand within nearly so short a period as six or eight hours. From 
these statements it might be thought difficult to distinguish between 
the effects of water and the weaker solutions; but in truth there is not 
the slightest difficulty until excessively weak solutions are tried ; and 
then the distinction, as might be expected, becomes very doubtful, 
and at last disappears. But as in all, except the simplest, cases the 
state of the leaves simultaneously immersed for an equal length of time 
water and in the solutions will be described, the reader can judge for 
himself. 
CARBONATE OF AMMONIA. 
This salt, when absorbed by the roots, does not cause the 
tentacles to be inflected. A plant was so placed in a solution 
of one part of the carbonate to 146 of water that the young 
uninjured roots could be observed. The terminal cells, which 
were of a pink colour, instantly became colourless, and their 
limpid contents cloudy, like a mezzo-tinto engraving, SO that 
some degree of aggregation was almost instantly caused , 
but no further change ensued, and the absorbent hairs were 
not visibly affected. The tentacles did not bend. Two 
12 
