448 NATURAL HISTORY OF PLANTS. 



extent more or less elongated spindles, rigid, pointed at both extre- 

 mities, and laid horizontally on the snrface of the leaves, where 

 they are kept hy a base of insertion corresponding to the middle of 

 their length or nearly so. The histologic organisation of the stalks is 

 also often qnite special in these plants, usually frutescent, very rarely 

 suffrutescent {Galjihimia., Camarea, Aspicarpa, Janima\ and often 

 climbing, by leaning against or twisting round trees, even to a great 

 height (Hipingc'). In these cases principally, the contours of the 

 woody zone are deeply sinuous, and these sinuosities are seen more 

 or less distinctly on the outer surface of the bark. The largest 

 bindweeds often have the form " of a cable composed of several cords 

 twisted together. They seem, at first sight, to result from the close 

 junction and torsion of several branches ; but a closer examination 

 does not justify this opinion, since, if each of these pretended 

 branches has its bark, the central one alone has a pith and medullary 

 sheath." A. de Jussieu (whom we have just quoted) attributes this 

 arrangement to the fact that, whilst in ordinary stalks the woody 

 bundles are, at all ages, developed in the periphery with uniformity, 

 the woody body of these bindweeds is unequally developed in dif- 

 ferent directions. Hence, the formation of lobes and interposed 

 cavities on which the bark moulds itself; the contour in contact 

 with this augmenting progressively in length, "whilst the junction 

 with the wood preserves its primitive dimensions, and even, if the 

 woody bundle separates a little in rising, this continuation, more and 

 more narrow, finally disappears." The interiJosition of layers of 

 cortical tissue to the more or less projecting and indepeadent seg- 

 ments of the woody body presents very great variations ; it may 

 even go so far as the total separation of the woody body into several 

 secondary masses, "thus giving to a single branch the appearance 

 of several, collected or twisted together.^ " The Malphjhiacea'^ like 

 many other bindweeds, are remarkable for the extreme development 



' See A. Juss. JI/»//«y/'. 9fi, t. 2. At the base 465. — Wigani), Ein. Bcisp. Jnom. Bild. des 



of the hair, or a little lower, the epidermis sup- Hokkorpcrs (in Flora (1856), 673, fig.). — Gau- 



porting it contains a gland, formed of siriall eel- dicu. Giiillem. Arch. Bot. ii. 502, t. 19; Meeh. 



lulos, often secreting an acrid, burning Hijuid, snr I'Orgiuiis. dcs Veget. t. 18 (11). — H. Mohl, 



the cavity of the hair becoming its very thick Xleb. d. Bau d. Rn»ki:n,-imd Schliiigpjlmi:en. Tii- 



coatcd reservoir. bing. 1827), ^ 75. — A. Juss. Coiiipt. Bend. Acad. 



" Maut. Qckhrt. ^jwi.7. (1842), 389.— LraoL. Sc. xii. 5-16; Ann. Sc. Nat. ser. 2, xv. 234 ; Mn/- 



[ntrnd. ta Bot. i. 212.— A. Rich. E/uin. Bot. ed. pigh. 100, t. 3.— Oliv. Stem, in Bicot. 1. 



in, 7n, fig. 47. — f'liuF.nEit, in Di.t. /cit. (1851), ^ In certain genera, like JTclcropleri/x (those 



