Boos I. ANOMALIES OF VEGETABLE DE VELOPEIMENT. 



177 



Sect. V. Anomalies of Vegetable Developement. 



781, A deviatioyi from the genei-al laivs of developement is occasioned by tlie intervention 

 of some accidental cause ; or of some cause operating permanently in certain subjects. 

 Hence the anomaly may regard the developement either of an individual or a species, 

 and may occur either in the root, stem, branch, leaf, bud, flower, or fruit, according to 

 the circumstances in wliich it is placed ; or it may affect the habit, duration, or physical 

 virtues of the plant. 



782. The root. According to the general laws of vegetable 

 developement, plants of the same species are furnished ^^-ith the 

 same species of root — not producing at one time a woody or 

 fibrous root, and at another time a bulbous root. And yet it is 

 found that there are cases in which changes of this kind do occur. 

 If part of the root of a tree planted by a pond or river, protrudes 

 beyond the bank so as to be partially immersed, it divides at tlie 

 extremity into innumerable ramifications, or sends out innumer- 

 able fibres from the surface, which become again subdivided into 

 fibres still more minute, and give to the whole an appearance 

 something resembling that of the tail of a fox ; wliich has ac- 

 cordingly been denonoinated by Du Hamel the fox-tail-root. 

 (fg- 57.) 



783. 77ie root of the Phleum prafense, when growing in a moist soil, which 

 it naturally affects, is uniformly fibrous ; but when growing' in a dry soil, 

 where it is also often to be found, it is furnished with a bulbous root. The 

 same is the case with the alopecurus geniculatus ; which, when growing 

 in its native marshes protrudes a fibrous root, though, when growing in a 

 very dry situation, as on the top of a dry wall, it is found to be furnished with an ovat-e and juicy bulb. 

 This anomaly also seems to be merely the result of a provision of nature by which the plant is endowed 

 with the capacity of collecting a supply of moisture suited to existing circumstances, and hence of adapt- 

 ing itself to the soil in which it grows. 



784. The roots of Utricutaria minor, which consist of a number of slender and hair-like filaments, exhibit 

 the singular anomaly of being furnished with a multitude of small and membraneous bladders, each con- 

 taining a transparent and watery fluid, and a small bubble of air, by means of which the plant is kept 

 floating in the water. 



785. "The descending root, an anomaly which attends some perennials, is at first spindle-shaped and per- 

 pendicular, sending out some lateral fibres ; but dying at the lower extremity in the course of the succeed- 

 ing winter, and protruding new fibres from the remaining portion, and even from the lower portion of the 

 stem, in the course of the following spring, which by descending into the soil, draw down the plant with 

 them, so that part of what was formerly stem is now converted into root. This process is repeated every 

 year, and by consequence a portion of the stem is made to descend every year into the earth. The 

 anomaly may be exemplified in the roots of Valeriana dioica, tanacetum vulgare, and oxalis acetosella; 

 and will also' account for the bitten and truncated appearance of scabiosa succisa, or devil's-bit. 



7Sfi. The beet-root, if dissected when about a year old, presents the singular anornaly of beijlg already 

 furnished with from five to eight distinct and concentric circles of longitudinal tubes or sap-vessels, im'- 

 beddcd at regular intervals in its pulp; whereas other biennial roots form only an individual circle each 

 year, and are, consequently, at no time furnished with more than two. 



787. yiigratory roots depend on a principle similar to the foregoing. If the stem of a descending root hap- 

 pens to be creeping or procumbent instead of being erect, then the lateral shoots from above are carried for- 

 ward in the direction of that procumbency , so that in the course of a few years the plant has actually changed 

 it-s place by so much as the stem has been converted into a root. This is well exemplified in the genus 

 Jris, which as it enlarges in circumference, dies in the centre and presents a ring of plants instead of a 

 solitary one. In the case of some aquatics, which float about on the surface of the water as they happen 

 to be driven by the winds, the whole plant may be said to be migratory, as in the case of the genus L,emna, 

 and some marine plants. 



788. Hoots changed to branches and branches to roots. If the stem of a young plum or cherry tree, biit 

 particularly of a willow, is taken in the autumn and bent so as that one' half of the top may be laid in the 

 earth, one half of the root being at the same time taken carefully out, but sheltered at first from the cold 

 and then graduallv exposed to it, and the remaining part of the top and root subjected to the same process 

 in the following year, the branches of the top will become roots, and the ramifications of the root will 

 become branches, protruding leaves, flowers, and fruit in due season. 



789. If the stem of a tree planted by a pond or river is so bent in its growth as to come 

 near to the surface of the water and to be occasionally immersed in it, it will sometimes 

 send out from the under surface a multitude of shoots that will descend into the water, 

 and develope themselves in the manner of the fox-tail-root. Sometimes it happens that a 

 stem, instead of assuming the cylindrical fonn common to the species, assumes a com- 

 pressed and flattened form similar to the herbage of the cactus as in the fir-tribe, ash, &e. 



790. The anomaty of the flattened stem {fig. 58. a) is accounted for by Du Ham.el by supposing that an 

 unnatural graft must have taken jilace in the leaf-bud ; and so united shoots that would otherwise 

 have been distinct. Sometimes the stem is disfigured by accidental tumors or bunches projecting from 

 the surface, and forming ultimately what are called knots in the wood. They are very common in 

 the oak and elm, and are produced perhaps by means of some obstruction in the channel of the sap's 

 motion, by which the vessels become convoluted and swell up into a bunch. 



791. But bunches are also to be met with on the stem of herbaceous plants, as on that of the carduus 

 pratensis ; of which you will often find a portion near the top swollen out into an egg-shaped or egg-oblong 

 bunch, extending from an incli to two inches in length, and about an inch across. If this bunch is cpt 

 open in the month of August, it will be found to contain several large and white maggots. It has conse- 

 quently been occasioned bv the puncture of the parent insect depositing its eggs. It does not seem to 

 affect the general health of a vigorous plant, though it might prove seriously injurious to a weak one. 



792. Bundled stem. Sometimes two or more contiguous stems, extending in the process of their 

 growth till they meet and press against one another, become incorporated at length into one, and form a 

 sort of bundle. This is what may be termed a natural graft, in opposition to an artificial graft, of whiclj 



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