CHANGES OF THE ORGANS OF PLANTS. 215 



upon the pistils of another ; the seed thus formed will produce a 

 plant resembling both. 



Varieties are a less important distinction than races ; they are not 

 continued by means of the seed, but produced by grafting or contin- 

 uation of the plant under some new circumstances. 



Variations denote the slightest kinds of difference ; they are occa- 

 sioned by peculiarities of cUmate, soil, moisture, dryness, &c. 



Degeneration or change of the Organs of Plants. 



The organs of plants, owing to peculiar causes, often experience 

 a metamorphosis, and instead of their usual appearance exhibit 

 anomalies, or vegetable deformities. 



We here use the term deformity, as signifying any variation from 

 the ordinary course of nature. The causes which produce these 

 changes are, 



1st. The adhesion of parts visually separate ; thus we often see 

 flowers, leaves, and fruits united, and appearing double. 



Some writers, among whom is the celebrated French botanist 

 De Candolle, assert, that a single petal which forms the corolla of 

 many flowers, as the stramonium or the blue-bell, is in reality com- 

 posed of several petals which become soldered, or cohere together 

 before the flower expands. The same writers consider a mono- 

 sepalous calyx to be composed of several little leaves thus united 

 before their development. 



2d. Changes are occasioned by a want of suflicient vigour in the 

 plant to bring all parts to maturity. Some of the seeds thus often 

 fail for the want of nourishment ; many plants which in one flower 

 produce several seeds, often ripen no more than one. The horse- 

 chestnut has six seeds, but seldom matures more than two ; in the 

 blossom of the oak where six seeds are produced, but one acorn is 

 perfected. 



3d. In some cases organs appear from certain changes to be inca- 

 pable of performing their original offices, and thus exhibit deformi- 

 ties; as where a bud, which, for want of sufficient nourishment, or 

 some other cause, does not develop itself into a leaf, but forms a 

 permanent protuberance or swelling upon the stem. The prickly 

 pear exhibits a thick and expanded stem, which is formed of leaves 

 imperfectly developed. 



4th. The stamens and pistils, through excess of nourishment, swell 

 and become petals ; all double flowers are formed in this manner. 

 The poppy in its natural state has many stamens, and but four pe- 

 tals ; but you often see double poppies, with scarcely the vestige of 

 a stamen left; the same change may be observed in the rose, which 

 naturally has but five petals and many stamens and pistils, but in a 

 very full double rose, scarcely any appearance of either stamen or 

 pistil is to be seen. The stamens, more frequently than the pistils, 

 meet with this metamorphosis, as they appear to be more intimately 

 connected with the petals. 



5th. The petioles or foot-stalks often change to leaves. This may 

 be seen in an Arabian plant. Acacia nilotica, which furnishes the 

 gum arable. This tree at first exhibits upon one petiole six or eight 

 pair of leaves ; this number every year becomes less, until all the 

 leaves disappear; the petiole then retaining all the nourishment 

 which before was distributed to the leaves, flattens and expands, and 

 appears in the form of a thick leaf 



Varieties— Variations— Changes of the organs of plants— Deformities— 1st cause of 

 the changes of plants— 2d cause of change— 3d case in which changes appear— 4th, 

 louble flowers, how caused— 5th, changes in petioles. 



