68 



NATURAL ins ran Y of plaxts. 



lived but a low montlis)' are usually better developed as tliey 

 approach tlie centre of the stem. In the Hellebores- and Anemones,' 

 the bundles, though of different ages, may form an apparently single 

 circle round a voluminous pith. In several herbaceous species has 

 been especially described the layer of cells called "protective s/ieatk."* 

 The axes of ManunculacecB are often, too, remarkable for the poverty 

 of their tracheal system. Moreover, a certain number of plants have 

 always been pointed out in this order as exceptional in the consistency 

 of the stem and branches being woody to a certain extent ; these are 

 chiefly the so-called " Tree-Pa3onies," Xanthorhiza, and Clematis. The 

 woody portion of the stem of Pceonia Moutan presents hardly any- 

 thing peculiar in its anatomy. The thick pith is surrounded by a 

 fresh ring of wood each season. The liber is, on the contrary, very 

 scanty, and the outer cellular layers of the bark are the seat of slow 

 and ill-marked exfoliation, much better seen in Xanthorhiza, and still 

 better in Clematis. In the former, beneath many layers covering one 

 another with great regularity, and in old brandies alternately white 

 and brownish — that is, dead and ready to peel off — may be seen a 

 layer of moniliform appearance, made uj) of cells, and gorged with, a 

 limpid yellow colouring matter.^ This structure, which is essentially 

 constant, assumes a high degree of distinctness and regularity in 

 Clematis, because the leaves are opposed, or verticillate ; and it has 

 here attracted the attention of very many observers.^ In the 

 hexagonal stem of Clematis may be seen a pith of no great thickness, 

 surrounded first by six, and then by ten, fibro-vascular woody 



' Tn tlie herbaceous shoots of Larkspurs a 

 month old we ni;iy tiiid them of three, four, or 

 five successive ages. 



* Link, Icon. Bot. Anat. (1857), ii. xi. 1, 5. 

 — L Dumas, op. cit., 5-23, t. 1, 2. — In H. 

 f(elidv.<t the pith is eiionnous, formed of cells 

 arranged in rows in every direction, so as to 

 form a network of beaded fibres separated by 

 irreguhir passages. The fibro-vascular bundles 

 ill a bhoot of a single season are numerous; they 

 are remarkaKle for having the whitish woody 

 fil)res surrounding the vessels on the sides as well 

 as external to them. The peduncle of II. niger 

 has the same fundamental organization. The 

 8ub-epidermic cortical cells are often gorged with 

 pink colouring matter. 



^ Vaupell, C. iib. d. periph. Wachsthum d. 

 Offaxhvnd. (1855), 21, t. 1. — The arrangement 

 of the bundles in the Anemones is funda- 

 mentally the same as in the annual Larkspurs. 



■• Caspaet, in Pringsheim's Jahrhuch. (1864), 

 iv. 101. 



* This yellow liquid is found in the young 

 wood, though of a paler tint. The liber of little 

 thickness, is incompletely divided into as many 

 closely packed segments, as there are sectors of 

 the wood (whose compact fibres are minutely 

 punctate), separated by the medullary rays. 

 The cells of the pith are also punctate. 



^ HUNDESHAGEX, ex MoHL {Ann. Sc. Naf., 

 scr. 2, ix. 295). — Duteochet, Accroiss. des. 

 Vcf/et. {Mem. Mus. (1821), vii. 397, t. 15, f. 



4-7). GlUOU DE BUZAREINGUES {Ami. Sc. 



J^'al., ser. 1, xxx. t. 7, figs. 3, 4 ; st'r. 2, 1, 159, 

 t. 5, fig. 1). — SciiLEiDEN, Grundzitge d. Wiss. 

 Bot. ii. 160, fig. 145.— QuEKETT, Histol. 84. — 

 Carpenter, Microsc. (1856), 431, 440 (? ex 

 Oliv.). — Griffith & Henfeey, Microgr. Diet. 

 (1856), 75, 387, 689.— A. Guillabd {Ann. 

 Sc. Nat., ser. 3, viii. t. xvi.). 



