PHYSIOLOGY. 995 
Barton found, that a solution of nitrat of potass 
had just the opposite effect. A few grains of it 
killed the Kalmia. Mr Brugmans, on the contrary, 
asserts, that nitrat of potass is an excellent stimu- 
lant to make vegetables grow. It is said that the 
Dutch gardeners make bulbs of Hyacinths, Nar- 
cissuses, and others, grow earlier by an addition of 
nitre. ‘Tromsdorff likewise found, that a sprig of 
the Mentha piperita became 378 grams heavier in a 
solution of nitre, whereas another sprig in common 
water, gained only 145 grains in weight. 
There is no doubt, that the decomposition of the 
water produces at the same time the peculiar tem- 
perature of plants, (§ 240). But the manner in 
which cold originates in them, has not yet been esta- 
blished. Sennebier and Hassenfratz believe, that as 
plants grow by decomposing the water, and com- 
bining the oxygen and carbon; the oxygen which 
thus becomes free, combines with the caloric of the 
vegetable fibre, goes off in a gaseous form, and 
produces the low temperature of plants. Mr Hum- 
boldt thinks, that plants take up caloric from the 
atmosphere, and with it give to the oxygen, which 
the light has separated, its gaseous form. From this 
he explains the: great coolness under the shadow of 
trees. 
That in the Fungi the process of inhalation and 
the separation of gases follow other laws, is certain. 
But we are so little acquainted with the nature of 
these vegetables, that we have not been able to fix 
those laws. Agaricus campestris and androsaceus con- 
YT 4 stantly 
