fall to 70° below zero; but that, if wind arise although the thermometer rise rapidly with it, the cold then becomes insupportable. These same voyagers acquaint us with an interesting fact, illustrating the truth of the old saying, that there is nothing new under the sun. Even the closed cases are as old as the creation. We are told, that the snow itself affords shelter to the productions of those inhospitable regions against the piercing winds that sweep over fields of everlasting ice. Under the cold defence of the snow plants spring up, dissolve the snow a few inches round, and the part above being again quickly frozen into a transparent sheet of ice, admits the sun's rays which warm and cherish the plant in this natural hothouse, until the returning summer renders such protection unnecessary. I need not, however, go to the Pole for illustrations of the effect of disturbed atmosphere in cold weather. One of our poets has said, 66 And, with east winds, will teach you how to shave.” All are familiar with our cutting March winds, which are so injurious and destructive to vegetation in the open air, but have no effect upon enclosed plants. With respect to change of air, the plants obtain all the change which they require, by virtue of the diffusion law already explained, and no method of closing the cases can prevent this from taking place. A few words respecting the importance of reflecting on what we see around us, will with propriety close the chapter.* The simple circumstance which set me to work must have been presented to the eyes of horticulturists thousands of times, but has passed unheeded in consequence of their disused closed frames being filled with weeds, instead of cucumbers and melons; and I am quite ready to confess that if some groundsel or chickweed had sprung up in my bottle instead of the fern, it might have made no impression upon me; and again, after my complete success with the ferns, had I possessed the inductive mind of a Davy or a Faraday, I should, in an hour's quiet reflexion, have anticipated the results of years. I should have concluded, that all plants would grow as well as the ferns, inasmuch as I possessed the power of modifying the conditions to the wants of each individual. * I was once honoured by a visit from a celebrated mathematician, who called to make inquiry concerning the management of plants in closed cases, as he had succeeded with some, but failed with others. He left me with these words. "Come and see me. I can in some measure repay you in kind. I can make you do what you have made me do-think." Inque novos soles audent se germina tuto VIRG. Geor. ii. 332. The golden boast Of Portugal and Western India, there The ruddier orange, and the paler lime, Peep through their polished foliage at the storm, COWPER. NUMEROUS have been the methods employed in the conveyance of plants to and from distant countries. It is quite unnecessary, however, to enter into any lengthened details of these attempts, as they resolve themselves into two kinds; the one, by which the plants are meant to be kept in a passive condition, and the other, by which means are employed to keep them growing during the voyage. |