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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 hygrometry — 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 faetidum, 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 " non fades omnibus una;" 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 micraniha 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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