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8 degrees higher. I was surprised, however, as well as delighted to find that the 
temperature of the water in the “ stem” in both cases was 68° Fah. It is obvious, 
therefore, that this equable temperature, of which the plant must necessarily par¬ 
take, is maintained by the equal ratio of evaporation, which will necessarily cor¬ 
respond with the measure of temperature in the atmospheric medium. It is thus 
that the plant will possess a medium temperature amid the vicissitudes and transi¬ 
tions of a fluctuating clime; having a remarkable correspondence with that com¬ 
pensation by which the animal machine is enabled to maintain a temperature of 
98°, whether traversing the snows of Lapland, or the sands of Nigritia. The 
overshadowing foliage of the tree, among the branches of which the Tillandsia 
takes up its abode, will contribute to the check of the cooling effects of radiation. 
There is, however, another fact, which I have experimentally ascertained, still 
more wonderful: as soon as the external air becomes dry and parched, the leaves, 
previously even air-tight at their junction, relax and open , and the water may be 
seen to trickle down the stem to moisten the roots. The Tillandsia , therefore, 
literally waters its own roots. 
Opening and Shutting of Flowers. 
At first sight, these phenomena would appear perplexed and somewhat difficult 
of solution ; but, in some cases at least, I have found that the question may be 
determined by experiments. The characteristic feature of the opening and shut¬ 
ting of the flower, is its dependence on Inygrometry —the moisture or dryness of 
the atmosphere. Towards evening, the flowers of the Ranunculus acris and 
Daisy gradually close and droop. The Anagallis arvensis is specially sensible of 
the coming shower, and multitudes among the numerous tribes of vegetation obey 
the same law, and must be familiar to all,—for instance, the blossom of Esch- 
scholtzia californica. If the common Everlastings, or the flowers of the Xeran - 
themum lucidum or proligerum, the Gnaphalium feetidum, or the shrubby Gna- 
phaliums of the Cape, the Ammobium alatum , and others be plunged into cold 
water, they will slowly close ; but when immersed into hot water, the petals 
instantaneously collapse. When the moisture evaporates in a dry and warm 
atmosphere, these flowers will as regularly open—experiments which I have often 
repeated with all of them; and so far the question seems sufficiently clear, namely, 
that the opening of the blossom is connected with a warm and dry state of the 
atmosphere, and its closure with a humid condition of the ambient air. 
But “nonfacies omnibus unaf there are not only exceptions, but the cases 
are numerous. When many plants go to sleep, some there are just awake; of 
this description is the Evening Primrose and its nocturnal associates. The Cereus 
grandiflora, and Stelis micrantha are exotics of a kindred character. So that 
beings are wakeful during the ordinary season of repose, both in the animal and 
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