DR. HOOKER ON WELW1TSCHIA. 155 



in the note referred to, assents to the proposition that " the 

 radicle is rightly regarded as an axis," i. e., an ascending 

 axis, " and not a root," but does not agree that it is an in- 

 ternode. To us, the one implies the other. Conceiving, as 

 we do, the fundamental idea of the morphology of the phse- 

 noganious plant to be, that the ascending axis consists of a 

 series of superposed internodes, each crowned by a leaf-bear- 

 ing point or ring (the node), the first internode must needs 

 be that which is crowned by the first leaf or pair of leaves, 

 the cotyledons ; and its whole development confirms this view. 



Dr. Hooker notes the curious fact that in Welwitschia 

 flower-buds are occasionally produced on the stock below the 

 insertion of the leaves, that is on the radicle or caulicle it- 

 self ; and Dr. Masters pointed out to him analogous cases of 

 shoots thus originating, one of which was described by Bern- 

 hardi thirty years ago. It is simply the case of adventitious 

 buds ; these might seem as likely to occur on the first inter- 

 node as on any later one. 



Welwitschia, having a dicotyledonous embryo, has also 

 essentially an exogenous stem, i. e., "the vascular system is 

 referable to the exogenous plan, but its arrangement into 

 concentric wood wedges is very rude." But the superadded 

 isolated and closed vascular bundles of the stock and root, and 

 especially their losing themselves in the periphery of the 

 stock, are endogenous analogies. So also is the strictly par- 

 allel and free venation of the leaves ; yet, as there are no 

 cross veinlets, thus favoring the splitting up of the leaf into 

 lacinise, this looks as much or more towards Cycadacem and 

 broad-leaved Coniferce. 



The total absence of anastomosing veinlets in the leaf, each 

 nerve representing a single and independent vascular axis, 

 extending, in Welwitschia, from the axis of the trunk to the 

 apex of the leaf, causes such leaves as these and those of 

 Dammara, etc., to " resemble more closely a series of parallel 

 uninerved leaves united by cellular tissue, than a foliar ex- 

 pansion of parenchyma traversed by one system of inosculat- 

 ing vessels, and the frequent presence of many linear coty- 

 ledons in these plants seems to favor this view, as does the 



