.'"JOS Jjmdon Unrtinillural Socictij and Garilrn. 



ICmlnrrnwiis mid Kxognwits Trees. — After hricily recapitulatiiis; tiic heads 

 of his former lecture, Mr. Lindley ohserved that the principle of adhesion 

 mav be termed the hinge of vegetable structure, since, perhaps, no other 

 science exhiliits in a more striking manner its effects. Besides its regular 

 operations, this principle often produces monstrosities ; two gourds, two 

 apples, or two peaches, growing close together, become united from 

 pressing constantly against each other. The flowers of the cockscomb 

 owe their singular shape to this princij)!e, as, in cases where it has been 

 prevented from acting, they liave been found to spread out into branches. 

 A similar monstrosity has been observed in the common asparagus ; and in 

 several other plants. 



Every plant is covered, except at the extreme points of its roots and 

 the upper surface of its stigma, with a membrane or cuticle, which, though 

 so extremely thin and fine as to be generally invisible to the naked eye, 

 is yti composed of parts adhering so firmly to each other as to admit of 

 its being peeled off. When viewed through a powerful microscope, this 

 men)brane is found to consist of cellular tissue studded with stomata; and 

 to appear streaked with a number of parallel lines, formed of rectangular 

 or irregular network. 



Every seed contains within itself a vital point, or axis, consisting of 

 two cones, which, in the process of germination, elongate themselves in 

 opposite directions ; one producing tlie stem, and the other the root. 

 These two parts being essential to all [)lants, Mr. Lindley proposed to 

 consider them separately. 



All stems, whether of herbaceous plants or timber trees, are subject to 

 the same general laws, and are all provided with leaf buds, by which only 

 varieties can be propagated. Buds are sometimes considered in the 

 nature of seeds, as they also possess a vital point from which both a stem 

 and a root will |)roceed ; but there is this essential diilcrence between 

 them, that from the one is raised a new plant of the parent tree, and from 

 the other a distinct individual. Leaf buds spring from nodes, or knots, 

 of which there are always several on every branch, at regular intervals. 

 ^Sometimes these nodes are placed exactly opposite to each other, and at 

 others at various distances, but always on alternate sides of the stem. 

 Whenever two leaves are foimd together on the same side, without one 

 occurring on the op[)osite side, it may be safely concluded that the missing 

 leaf hjifi been removed by some accidental circumstance. The spaces be- 

 tween the nodes are called internodes, and these intervals are of irreguhir 

 length; generally, however, becommg shorter towards the extremity of the 

 branch, liuds are sometimes I'ound on the internodes, but, when they 

 are, the circumstance must be considered as a kind of lusus naturae, and 

 not as a general law. 



Each Iciif forms with the stem an axil, in which is found an axillary 

 bud. Buds are covered with scales, generally dry and brown, which 

 drop off" as the leaves unfold themselves. There is sometimes a second, 

 and even a third and fourth, set of scales, of various tinges of white, brown, 

 and red, fount! enveloping the inci[)ient leaves. All, however, no sooner 

 expand, than they drop olf. 



JJuds are sometimes loinid upon leaves. The fragments of a leaf of a 

 species of Ornithngalnm, laid upon moist ground, produced buds, not only 

 on the edge of the leaf, but on its siu'face ; ami a few plants produce buds 

 on tlieir leaves naturally. Among these may be mentioneil the Maliixis 

 pahidosa, and the Bryophsllnm calyciiuun. 



I'laiits are irivided into two classes, with regartl to the internal structure 

 of the stem : viz., the endogenous, or such as increase inwardly ; and the 

 exogenous, or such as increase outwardly. The former do not enlarge 

 their bark, or outer circiunference, after a certain point, but gradually fill 

 up their interior by successive dej)ositions of fibrous matter, which, in the 



