PROCEEDINGS OF SOCIETIES, 283
tion th<it tills arose from the fusion of two bundles back to back. He li.id himself ascertained the occurrence of extremely large scalariform ducts in SiiiUax. It was evident that geologists should be careful in de- termining plants from the nature of the vessels. Professor Wyville
Thomson said that the chain-like crystal-bearing tissue would, if it proved characteristic oF Screw-pines, be a valuable menus of determining {\w, na- ture of some fossil monocotyledoiious stems. Neil Stewart, " Observa- tions on the Intimate Structure of Spiral Ducts in Plants, and their Kelationship to the Flower." It is to be regretted that this pap;^r was permitted to be read. It exhibited a fundamental misconception of the most elementary points in vegetable minute anatomy. A considerable portion of the paper was devoted to the description of "a vascular system" within the epidermal cells of a Hose-petal, "rivalling in com- plexity the structure of the human eye." [A reference to Carpenter's ' The Microscope,' 4th edition, p. 425, will show what the author really attempted to describe.]
Augimt 8. — Professor Balfour, " On the Cultivation of Tpccacuanlia in the Edinburgh Botanic Garden for transmission to India." Besides the plant which had long been in the garden, what was apparently another species had been received from Dr. Gunning. It resembles more than the garden plant the figure of Martins. The leaves were more pointed
and less leathery. Professor W. C. Williamson, " On the Classification
of the Vascular Cryptogamia, as affected by recent Discoveries among the Fossil Phints of the Coal-measures." The author thought that justice had never been done to Professor King, of Galvvay. He did not say that his paper (' Edinburgh New Philosophical Journal,' 1844) was accurate either in details or in its broad features, but thought, nevertheless, that the value of the communication had never been recognized. He wished to insist on the exogenous growth of the woody axis belonging to stems of the Carboniferous Cryptogams. In Calamites, which, though not ex- actly Ecpiisetaceae, were tiieir representatives, the central pitli was sur- rounded by a cylinder of wedges resembling those of young Dicotyledons. These wedges sometimes not less than two inches in thickness, and wholly vascular, were a clear proof of exogenous growth. Amongst Lycopodia- ceous plants, Adolphe Brongniart distingnished Lepidodendroid and Sigillarian plants. In Sigillaria there were two distinct zones, but in Lepidudendron there was no such arrangement; these he I'egarded as Ly- copodiacea, but Sigillnrins as gyninosperms. However, he (Professor Williamson) was in a position to show that in Lepidodeiidron there is a representative of the second ring. Lepidodendron, according to his view, lias a vascular pith, surrounded by a true woody zone, from which bundles are given oif. The specimen had been carefully figured by Carrnthers, though he differed from him in details, especially in asserting the existence of medullary ra\ s. There was a very elaborate cortex, very corky in some plants, very fibrous in otiiers. The Sujillarin vascularis, of Binney, in- cludes two forms, one in which the medulla is dilfercntiated into medul- lary cells, and peripheral vessels ('medullary zone'), and the woody zone exhibits mechillary rays. The Dlploxj/Jon of Corda, has proved tiiat' ravs do not proceed from the medulla, but from the woody zone. In Stigmaria he also maintained that the vascular bundles proceeding from rootlets are derived from the cylinder and not from the medulla. In these plaids, as an evolutionist, he looked upon the ' medullary zone' as corresponding to the
�� �
