126 



HISTORY OF THK VKGETABLE KINGDOM. 



ing the degree of heat. Hence pknts occupying 

 the polar regions, and plants growing on the 

 summits of high mountains of southern latitudes, 

 are in floorer at the same season. And hence 

 the same species of flowers are later of blossom- 

 ing in North America, than in the same latitudes 

 in Europe, because the surface of the earth is 

 higher, or the winters 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 always 

 ripen its fruit the soonest. The hazel tree, wliich 

 blows in February, does not ripen its fniit till 

 autumn, while the 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 currant and gooseberry; 

 if it blows in summer, it ripens its fruit in 

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

 blows in autumn it ripens its fruit in winter. 

 But the meadow saffron, which blows in the 

 autumn, does not ripen its fruit till the succeed- 

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

 a Calendar of Flora might be formed. They 

 have not hitherto been very minutely attended 

 to by botanists, and perhaps by many may be 

 [■eckoned 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 sufficiently striking as to have attracted the 

 attention even of savages. Thus, some tribes of 

 American savages act upon the very principle 

 suggested by Linnaeus, and plant their corn when 

 the wild plum blooms, or when the leaves of 

 the oak are about as large as a squirrel's ears. 

 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 strawberry month, 

 and anotherthe mulberry month; and theautumn 

 is designated by a term signifying the fall of the 

 leaf. 



There are also several other waj's 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 cii-cumstances 

 the leaves of the Indian mallow become concave, 

 and it seems as if tlie effect were produced 

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

 because the same effect may be produced even 

 bj' 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, exr 

 hibit a singular phenomenon even in the common 

 foot-stalk, which is found 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 observa- 

 tions of Du Hamel, 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 

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

 with the lower part of the stem at noon, it 

 formed an angle of 212°; at three 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- 

 getlier. But this opinion requires some limita- 

 tion; for some plants exjjand 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 

 ofi^ 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 infen-ed 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 pai'ent trees. 

 Du Hamel planted some young trees in the 

 autumn, cutting off aU 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 uniformly 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 frozen 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 

 preservation 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 shall render their motion 

 evident to man, as well as that expression of the 

 whole plant, which is the most evident token of 



