88 MR. D. OLIVER ON SYCOPSIS, A NEW GENUS OF HAMAMELIDE^. 



in 1835*. From an examination of the wood of this species, and of a second undescribed 

 Malayan BucJdandia (?), of Bliodoleia, Trichocladus, Hamamelis, Sycopsis, Eustigma, 

 Distijlium, Corylopsis, and Liquidambar, I find a close uniformity throughout in respect 

 to its minute structure. The more or less circular and faintly defined disks of the often 

 much elongated and tolerably thick-walled prosenchyma of the wood are, as in the Coni- 

 fer ce, due to the presence of minute lenticular cavities between the adjoining wood-cells : 

 the canals traversing the secondary layers of these cells are opposed on each side to 

 these intercellular spaces, and are almost invariably elongated laterally in a direction 

 transverse or oblique to the axis of the cell, although sometimes nearly circular and 

 very minute, and then in all respects quite similar to those of the so-called " glandular 

 markings" of coniferous woodf. In all the HamameUdecB examined I have found a 

 proportion of vessels in the wood fully equal to that obtaining in the more familiar Dico- 

 tyledonous structm-es; in some {Corylopsis for example) the vessels in a cross section of 

 the wood, occupy an area about equal to that of the other tissues. Generally the vessels 

 are transversely barred. The medullary rays are numerous and narrow, consisting of 

 plates of but one cell (though often of two or three) in thickness. In the present state of 

 knowledge, it would be useless to speculate on the purport of the intercellular spaces 

 which constitute the peculiarity of the wood of these plants ; nor can we indicate how far an 

 identity of structure in this particular alone with that of Gymnosperms afPords a ground 

 for the notion that, possibly, through a long-continued series of widely receding diver- 

 gences in respect to aU the reproductive apparatus, the histological character of the 

 elementary tissue of the vegetative organs might afford a contrasting constancy. 



If, however, connecting links between these remarkably different groups ever existed, 

 assuredly none now remain. If the tissue characteristic of Gymnosperms has been 

 rightly designated by a distinguished naturalist "the highest specialized tissue known J" 

 (I presume, on the ground of its discoid markings), it does become of some interest to 

 trace a close approach to it throughout a group presenting in hardly any other respect a 

 single feature in common. In the absence, however, of vessels from the dense bundles of 

 prosenchyma of the cone-bearing Gymnosperms (in which the markings are especially well 

 developed), although their r61e is almost as obscure to us as that of the interspaces of the 

 wood-cells, I should scarcely regard this tissue as offering, in its structure, a higher 

 measuxe of specialization than obtains in the little order under consideration. 



* Private Journals, p. 4. 



t In some Gymnosperms, however, the canals are often thus elongated, and become slit-like, as occurs in Callitris 

 and Araucaria Bidivcllii. In Salisluria the disks are irregularly scattered and small. 

 X Dr. Hooker in ' Essay on the Flora of Australia,' p. xxii. 



