VAUCHERIA. 



[ 670 ] 



VAUCHERIA. 



progressive bundles; but as no new develop- 

 ment occurs in these in successive seasons, 

 they are further distinguished as definite 

 bundles from those of the Dicotyledons. The 

 structure of the vascular bundles of Monoco- 

 tyledons is very well seen in different charac- 

 teristic conditions, in vertical and horizontal 

 sections of the stems of the white lily, of the 

 large grasses, rhizomes of sedges and rushes ; 

 affording well- developed examples in herba- 

 ceous structures ; of the bamboo (an arbo- 

 rescent grass), of the common cane or the 

 " partridge cane " (both species of Palms), 

 where the bundles are connected by lignified 

 parenchyma. In leaves of bulbous Monoco- 

 tyledons, &c., the bundles consist chiefly of 

 spiral vessels; in the palms, bananas, &c., 

 the woody fibre extends also into the ribs of 

 the foliaceous organs. 



In the Dicotyledons, the bundles of the 

 stem appear first as a circle of cords com- 

 posed of spiral vessels, around the pith, out- 

 side which larger vessels and ducts, and sub- 

 sequently woody fibre or wood-cells are 

 developed, passing into the elongated pros- 

 enchymatous liber (fig. 797). The develop- 

 ment of the successive regions is progressive 

 during the first season ; but here the cam- 

 bium layer remains capable of renewed 

 activity, and a new layer of wood (and of 

 liber) is added on the outside of the bundle 

 in each successive season ; hence these bun- 

 dles are distinguished as indefinite. These 

 may be observed in sections and young 

 shoots of any common tree (figs. 459 & 461, 

 page 419). 



Infinite variety of modification occurs in 

 the character and arrangement of the vas- 

 cular bundles within the limits above laid 

 down, or very slightly overstepping them. 

 A few remarkable cases may be mentioned 

 here ; in the Orobanchacese (parasites) no 

 spiral vessels occur in the vascular bundles 

 forming the wood; in Victoria regia the 

 isolated bundles are composed of spiral 

 vessels without any prosenchymatous wood- 

 cells ; other peculiarities, influencing more 

 especially the characters of WOOD, are given 

 under that article. (See also CAMBIUM and 

 MEDULLA.) 



BIBL. Works on Structural Botany. 



VAUCHERIA, D.C. A genus of Sipho- 

 nacea3 (Confervoid Algae), consisting of green 

 filamentous plants growing in fresh and salt 

 water, and on damp ground, characterized 

 by the continuity of the cavity throughout 

 the branched tubular filament (sometimes 

 several inches long) of which each plant is 



composed, and by the modes of reproduction, 

 both by gonidia and by spores. Vaucherice 

 may be gathered on damp borders in 

 every garden, or by the sides of ditches, 

 where they form fine silky green tufts; they 

 are very variable in form and size, so that 

 the specific distinctions heretofore laid down 

 appear to be worth little. The ordinarily 

 occurring species presents itself as a tubular 

 cell, of comparatively gigantic dimensions, 

 containing more or less protoplasm, coloured 

 by chlorophyll, in the form of minute gra- 

 nules, applied upon th,e wall, or occupying 

 more or less of the cavity. The green gra- 

 nules may be seen to lie imbedded in a 

 colourless protoplasm at the inner surface 

 of the cellulose wall; and it is curious to 

 observe, when the filament is accidentally 

 or intentionally ruptured, that the green 

 granules which may escape are contained in 

 a mucous investment which soon rounds 

 itself into a globular body, of size propor- 

 tionate to the quantity of green granules 

 extruded; these globules even exhibit a 

 slight rolling movement sometimes, but they 

 appear ultimately to decay. Such globules 

 sometimes occur inside the filaments, when 

 the growth is unhealthy, and Itsigsohn calls 

 them spermatospheres, stating that they pro- 

 duce spermatozoids. This, like all this au- 

 thor's observations, requires confirmation. 



If the Vaucheria filaments are gathered at 

 a favourable epoch, or if they are cultivated 

 in a vessel of water well exposed to light, 

 the blind ends of the filaments (or rather of 

 the ramifications of the filament) are found 

 very densely filled with green contents, ap- 

 pearing almost black ; and if these ends are 

 watched early in the morning, a remarkable 

 series of phenomena is observed in them. 

 The ends of the filaments about to produce 

 gonidia are found swollen into a slightly 

 clavate form; the green contents of the 

 "club" part from the general contents of 

 the filament, leaving a transparent space 

 (fig. 798) ; then, having as it were acquired 

 a definite independence, the isolated mass 

 returns so as to fill up the transverse light 

 space, but does not again coalesce with the 

 lower mass of contents. Next a light space 

 is observed between the surface of the ter- 

 minal body of contents and the cellulose 

 wall surrounding it, and the latter soon 

 gives way at the apex, forming a passage for 

 the escape of the contents. This mass of 

 contents is now clearly recognizable as the 

 gonidium or zoospore; it gradually extri- 

 cates itself from the tube, with a rotatory 



