310 



PHY 



THE UNIVERSAL HERBAL; 



PHY 



them in warm climates remain from three to six years on the 

 branches. A few in colder climates, and only those which 

 have a tenacious sap, as Ilex aquifolium and Viscum album, 

 or such, which have sap of a resinous nature, as all the 

 Pine-tribe trees, retain their leaves during winter. All other 

 plants of the colder climates drop their leaves in autumn. 

 This happens in many different ways. Some leaves decay 

 gradually, and fall off, or remain on the stem in a dry state 

 till spring; others fall off when still green, even in the mild 

 serene days of autumn. In quite a different manner the 

 Robinia pseudacacia parts with its leaves. The pinnate leaves 

 of this tree first drop, then all the pinnulae, and at last, after 

 them, the petiole to which they adhered drops off. The 

 cause of the falling off of the leaves is this : During the 

 summer the vessels of the petiole become gradually ligneous, 

 as the sap is conveyed to them in greater quantity, and the 

 whole frame of the leaves gets a more ligneous consistence. 

 The sap must in consequence gradually stagnate, and at last 

 the communicating substances between the stem and the 

 petiole are completely shrunk. The wound which the stem 

 thus receives cicatrizes before the petiole separates. The 

 connection now interrupted between the leaf and the stem, 

 and their vessels, causes the petiole, by which they are con- 

 nected, to separate entirely, and thus, especially in calm 

 serene weather, the leaves unavoidably fall off. For as the 

 rays of the sun still favour the last decomposition of the 

 water, and the reducent vessels cannot convey the small 

 quantity of moisture to the knot of the petiole, the motio'h 

 of the small quantity of sap naturally remaining will cause 

 some sort of concussion, which is sufficient to occasion the 

 fall of the leaf. In the Oak-tree the leaf cannot fall off in 

 autumn, as the vascular fibre of this tree is very tenacious, 

 and on this account the connection between the knot of the 

 petiole and the stem is not broken. In the Robinia pseuda- 

 cacia, the small and tender petioles of the leaves first are 

 closed up, and -separate of course earlier from the common 

 petiole, which is still succulent enough to remain a short 

 time, but soon, as without the leaves it cannot subsist, has 

 the same fate. It depends, therefore, entirely on the nature 

 .of the leaf, how long it is to remain on the stem, and by no 

 means on the weather. The peculiar organization must not 

 be overlooked, as it really has a powerful influence. 



" The growth of the plant ends with the evolution of the 

 flower. When a plant has acquired a certain degree of firm- 

 ness, (which, as they are so multifarious, does not happen in 

 each at the same time, or in the same age,) it then becomes 

 capable of propagating its own species, and that part which 

 we call the flower is now formed.' Its speedy appearance- in 

 herbaceous plants, may generally be observed from the cir- 

 cumstance, that the minute scaly leaves grow gradually less, 

 till the smaller and more delicate parts of the flower are at 

 last unfolded. Goethe is therefore not mistaken, when he 

 calls the growth of plants a contraction and expansion; an 

 idea which Wolfe already has endeavoured to prove. The 

 flower is, as all the other parts of plants, formed by spiral 

 vessels, which, as soon as the first rude sketch, as it were, of 

 the flower exists, are already observable. Linneus formed a 

 very erroneous idea on this subject. He considered the pith 

 of a plant, which he believed to be of equal importance with the 

 spinal marrow of animals, as the sole formative organ in the 

 whole vegetable kingdom. Vegetation in general, according 

 to his opinion, went on by means of the pith. The seed itself 

 was a small piece of pith,, which separated from the mother 

 plant, on purpose to go through the same revolutions as the 

 old plant had done. But he proceeded still farther, and 

 ascribed to each part of a plant a certain peculiar power in 



forming one part of the flower. The calix was formed by the 

 bark, the corolla by the inner bark; the stamens were formed 

 by the wood, and the pistils by the pith. He carried this 

 ingenious hypothesis still farther, by asserting, that in ligneous 

 plants each branch required five years for the final evolution 

 of the flower, and that each year something was added to 

 the future flower. In the first year, for instance, the scales 

 are formed, when the branch is shooting out from the bud ; 

 in the second year the calix ; the corolla in the third ; in 

 the fourth the stamens ; and in the fifth the whole, for the 

 formation of which nature required all that time, is com- 

 pletely evolved. Linneus may be right so far, that plants 

 require a certain time to blossom ; that in them previously a 

 great quantity of sap, which has been so carefully elaborated, 

 as to become capable of forming parts so important for the 

 continuation of the species, is first laid up; but that every 

 year any one part of the flower, as an effort, is produced, 

 would be very difficult to prove. As little can we suppose 

 that the pith alone is the only formative part in plants. It is 

 clear from the account of its use and design, that it may be 

 wanted; which is contrary to the old opinion. But that the 

 cortex, inner bark, wood, and pith, &c. should each form a 

 peculiar part of the plant, is so much against common expe- 

 rience, that it is hardly necessary to refute it. We find in 

 the springing flower, elongations of spiral vessels, but wo 

 never see elsngations from each particular part, one forming 

 the future calix, another the Corolla, and so forth. For 

 instance, in the Common Sun-flower, (Helianthus annuus,) 

 where on a large receptacle, numerous small flowers are 

 placed, how should those elongations be able to unfold them- 

 selves into florets from the bark, inner bark, &c. through 

 such a receptacle ? There would arise a confusion amongst 

 those small parts, which is never met with. Further, how 

 should the stamina be produced in herbs, which are not lig- 

 neous? or the pistil, in plants which have no pith? Who 

 does not see that all these assertions are mere hypotheses, 

 which may be refuted even without the aid of anatomical 

 investigation ? The flower does not always appear in the 

 angles of the leaves or at the extremities of the stem, but 

 in some plants it shoots forth in very uncommon places. 

 Rohria petioliflora has its flowers situated on the petiole. 

 This is also the case in Salsola altissima, and some other 

 plants. In most species of the genus Ruscus, the flower is 

 found in the middle of the leaf. Most species of Phyllan- 

 thus, Xylophylla, Polycardia, and one species of Ruscus, 

 R. androgynus, flower on the margin of the' leaves. On 

 branches which are leafless appear the flowers of Cynometra 

 ramiflora, Ceratonia siliqua, Averrhoa bilimbi, and A. caram- 

 bola, Bcehmeria rumi flora, and other plants. Most remark- 

 able is the station of the flower in a tree of the East Indies, 

 called Cynometra cauliflora. This very leafy tree has no 

 flowers but at the foot of its stem ; its leafy top never pro- 

 duces any. 



" The flower, consists of the calix, corolla, nectary, stamens, 

 and pistils. The calix and corolla are, in point ot the distribu- 

 tion of their vessels, exactly like the leaves. The calix, when 

 green, transpires, like the leaves, oxygen gas in sunshine; 

 but when it is coloured this does not take place. Both these 

 parts imbibe their necessary support from the air, and convey 

 it to the receptacle on which the flower is placed. The func- 

 tions of absorption and transpiration are performed by the 

 leafy parts of the flower as well as by the leaves of the plants. 

 Only the coloured flower emits other gases. Hitherto it has 

 not been determined, whether the phenomenon which the 

 Dictamnus albus presents in warm serene summer nights, 

 when there is no moonshine, is produced by hydrogen gaa, 



