126 



HISTOUY OF THE VEUETABLE KINGDOM. 



Ing the degree of heat. Hence plants occupying 

 the polar regions, and plants growing on the 

 summits of high mountains of southern latitudes, 

 are in flower at the same season. And hence 

 the same species of flowers are later of blossom- 

 ing in North America, than in the same latitudes 

 ill Europe, because the surface of the earth is 

 higher, or the wintere more severe. 



There is also much diversity in the degree of 

 warmth, and its duration necessary for the ma- 

 turation of the fruits of vegetables, as well as 

 for their frondescence and flowering. But the 

 plant that flowers the soonest, does not alwaj-s 

 ripen its fruit the soonest. The hazel tree, which 

 blows in February, does not ripen its fruit till 

 autumn, while tlie cherry, which does not blow 

 till May, ripens its fruit in June. It may be 

 regarded, however, as the general rule, that if a 

 plant blows in spring, it ripens its fruit in sum- 

 mer, as in the case of the cuiTant and gooseberry ; 

 if it blows in summer, it ripens its fniit in 

 autumn, as in the case of the vine; and if it 

 blows in autumn it ripens its fruit in winter. 

 But the meadow saff'ron, which blows in the 

 autumn, does not ripen its fruit till tlie succeed- 

 ing spring. Such are a few of the facts on which 

 a Calendar of Flora might be fonued. They 

 have not hitherto been very minutely attended 

 to by botanists, and perhaps by many may be 

 reckoned more curious than practically useful. 

 At all events, all such records afford pleasing 

 associations connected with the ever varying 

 phases of the year, and the phenomena are at 

 least sufiiciently striking as to have attracted the 

 attention even of savages. Thus, some tribes of 

 American savages act upon the very principle 

 suggested by Linnteus, and plant their com when 

 the wild plum blooms, or when the leaves of 

 the oak are about as large as a squirrel's em-s. 

 The names of some of their months are also de- 

 rived from the stages of vegetation. One is 

 called the budding month, and another the 

 flowering month; one the strawbeiTy month, 

 and another the mulberry month; and the autumn 

 is designated by a term signifying the fall of the 

 leaf. 



There are also several other ways in which 

 the agency of heat may be observed, as exciting 

 the vital energies of plants. Thus, the leaflets 

 of some of the leguminous plants, when exposed 

 to the action of an ardent sun, are often erected 

 into a vertical position on each side of the leaf- 

 stalk, which they sometimes even pass, so as to 

 close together. Under similar circumstances 

 the leaves of the Indian mallow become concave, 

 and it seems as if the efi^ect were produced 

 merely, or at least chiefly, by means of heat, 

 because the same effect may be produced even 

 by means of the application of a hot iron; and 

 yet the leaflets of many such plants fold them- 

 selves back at night, so 'as to meet under the 



leaf-stalk. Several species of mimosa also, ex- 

 hibit a singular phenomenon even in the common 

 foot-stalk, which isfound to have a sort of natural 

 movement dependent upon the temperature, so 

 that it is elevated in the course of the day, and 

 depressed at night. According to the obsen'a- 

 tions of Du llamel, at nine o'clock in the morn- 

 ing of a September day, the weather being mo- 

 derately fine, the foot-stalk of a leaf of mimosa 

 pudica, formed by its position an angle of 100°; 

 with the lower part of the stem at noon, it 

 formed an angle of 212°; at tlu-ee in the after- 

 noon it had fallen to an angle of 100°; and dur- 

 ing the night it fell to an angle of 90°, thus in- 

 dicating an evident susceptibility to the stimulus 

 of heat. 



As a summer heat is necessary to the full 

 and perfect exertion of the functions of vege- 

 tables; so the depression of temperature conse- 

 quent upon the cold of winter, has been thought 

 to suspend the exertion of those functions alto- 

 gether. But this opinion requires some limita- 

 tion; for some plants expand their leaves and 

 flowers even in winter, such as many of the 

 mosses ; and others develope their buds during 

 this season, in which there is a regular and 

 gradual progress of vegetation till they expand 

 in spring. The sap, it is true, flows much less 

 freely, but is not entirely stopped. Hales lopped 

 ofl^ some branches from the hazel, and vine, and 

 jessamine, respectively, in course of the winter, 

 and covered the section of the separated branches 

 with mastic; and in a few days these branches 

 were found to have lost considerably in weight; 

 whence he inferred the motion of the sap, be- 

 cause it seems reasonable to suppose, that this 

 dissipation of sap would have been repaired, il 

 the branches had remained on their parent trees, 

 Du Hamel planted some J'oung trees in the 

 autumn, cutting ofl^ all the smaller fibres of the 

 root, with a view to watch the progress of the 

 formation of new ones. At the end of every 

 fortnight he had the plants taken up and ex- 

 amined with all possible care, to prevent injuring 

 them; and found, that when it did not actually 

 freeze, new roots were unifonnly developed. 

 Hence it follows, that even during the period of 

 winter, when vegetation, to all appearance, seems 

 totally at a stand, the tree being stripped of its 

 foliage, and the herb apparently withering in 

 the fiozen blast, still the energies of vegetable 

 life are exerted, and still the vital functions are 

 at work, carrying on, in the interior of the plant, 

 concealed from human view, and sheltered from 

 the piercing frosts, operations necessary to the 

 presei-vation of vegetable life, or development of 

 future parts ; though it requires the returning 

 warmth of spring to give that degi-ee of velocity 

 to the juices which sliall render their motion 

 evident to man, as well as that expression of the 

 whole plant, which is the most evident token of 



