64 NATURAL HISTORY OF PLANTS. 



one another by medullary rays. In each bundle the liber is repre- 

 sented in section by a crescent, outside of which is another cor- 

 responding to part of the generative zone. More internally is the 

 woody part of the bundle forming a triangle with its acute apex 

 inwards. The relative distribution of the vessels and fibres is 

 singular : the former, on the whole rather irregularly arranged, are 

 so placed as to be surrounded by fibres on every side, especially on 

 the inside." Besides the scattered vessels there is a central linear 

 series in each bundle. The tracheae are very scanty in the medullary 

 sheath. But towards this side of the bundle the woody fibres become 

 very numerous, dotted and perforated, and they are internal to the 

 parts that usually constitute the medullary sheath. 1 In the medul- 

 lary rays is green matter, which also exists at first in the peripheral 

 cells of the pith. " Outside, the medullary rays are continuous, 

 without any line of demarcation between the wood and the bark, 

 passing between the liber bundles. It is in the substance of the 

 short unequally fusiform fibres that constitute these bundles that we 

 find the bitter yellow limpid colouring matter whose presence 

 characterizes all the species of Berberis:" 



The second type is that of the Podopliyllece, whereof R. Brown 

 noticed 3 that Podophyllum, like D/phy/leia, has in its stem irregularly 

 scattered fibrovascular bundles ; so that in this respect their structure 

 approaches far more nearly that of a Monocotyledon. 4 In transverse 

 section we find in the common cellular matrix spots representing the 

 sections of as many isolated fibrovascular bundles, which are more 

 slender as they are more external, and are only absent in the centre. 



1 These fibres cannot be regarded as other than softness of the liber bundles as compared with 

 woody fibres, for though they present several the woody consistency of the interposed parts of 

 differences in length and thickness, we find every the medullary rays. 



possible transition. The tracheae are very few in 3 Congo, 442, not. ; Misc. Works, ed. Ben.v, 



number, lying among the most internal vessels of i. 124, note i. 



each layer. 4 J. G. Agardh (Theor., 75) says he has found 



2 The sarmentose stems of the Lardizabalece that the stems of Podophyllum and Diphylh-ia 

 are formed on the same general plan. They are organized completely, as in Monocotyledons, 

 are remarkable for the clearness of the medullary "... fasciculos nempe vasorum omnes medvl- 

 rays, for the form and freedom of the liber lares et sparsos, singulos vero strato prosen- 

 bundles, and for the tardy multiplication of the chymatoso ambientc, vasisque cambialibus ex- 

 fibrovascular bundles, which recalls what occurs in trorsum, et spiralibus introrsum dispositis, coii- 

 Menispermacece. In Stauntonia Lindley men- stitutos. Biphylleia strato corticis aliquantulum 

 tions the curvature of the medullary rays (Intr. magis evoluto tantum a Podopl/yllo distat. 

 to Bot., i. 213). Is this normal ? In pretty old Monocotyledonea hac caulis structura Podo- 

 stems of Akebia qulnata we saw these rays phyllece ad Xgmpltceaceas tendere forsan 

 straight. We also notice the thickness and videntur." 



