EQUISETUMS AND CALAMITES, 85 
rows of thickened dark-brown parenchymatous cells are found, the 
outer cells being empty, while the inner. are filled with starch, and 
passing into thin-walled, colourless, starch-bearing parenchyma more 
several are present, being largest. Surro 8, soft- 
walled cells fill e space. lls fo the phloem 
part of the bundle, and consist of parenchymatous cells 
parenchyma) and cribriform eells. e fibro-vascular bundle is sepa- 
rated from the cortical tissues by the sheath of the fibro-vascular 
bundles. 
uctuRE oF CatamiTEes.—The resemblance between the vege- 
tative parts of Equisetums and Calamites is no mere superficial one. In 
the Calamites there existed alarge underground stem running for a 
considerable distance and giving off aerial shoots. Such being the 
nous Fi aes a deep-seated origin) buds Pe a single 
cell in the tissue at the base of the fasinates “nerdy leaves, 
en we can easily see how they became detached, the attachment 
i ys 
being so slight : not as in Dicotyledons and Perinat ati y a direct 
passage of the stem tissues into those of the branch, or by true iP eagcoe 
ms and Lycopods. The erect aerial stems would be m 
The Calamite stem, both aerial and subterranean, possessed a central 
lacuna or fistular sith similar be hang in the quisetums of the present 
day,* and around this central lacuna the fibro ar bundles are 
placed in a circle ebsites g chose i in n the stem of A essing g Dicotyledon. 
Tt is to the structure of these bro-vascular bundles that I wish to 
separated by a lit 
parently prolonged externally, and forms a wedge-shaped 
masses uniting externally and forming a continuous layer exactly like 
the wood of a pe ba old Dicotyledon. In this mass the cells have 
& more or less ting linear arrangement, wi with smaller cells between 
the larger ones. Here i in nearly all known specimens the tissue ends, 
* Prof. Williamson states (op. cit., p. 505) that the pith of the present sub- 
terranean, rhizomes of thé Equisetums remains intact, not even becoming fistular. 
