io8 



VASCULAR CRYPTOGAMS 



of a large amount of sulphates, and the total absence of alkaline carbon- 

 ates. 



A large portion of the parenchymatous fundamental tissue is desti- 

 tute of chlorophyll ; it is only in the vegetative aerial shoots that there 

 is any considerable development of chlorophyllous tissue, and then it is 

 usually situated in the furrows beneath the stomates. The ' vascular ' 

 bundles of Equisetum are collateral, and are much less strongly lignified 

 than those of ferns. They lie in a circle between the medulla and the 

 cortex, between and somewhat within the cortical canals, and necessarily 

 run parallel to one another. As will be seen from the description given 

 above, each bundle is the result of the coalescence of two branches, one 

 of which originates in the leaf-sheath, while the other develops in the 



Fig. 82. — Stomate of ^. hyeviatel^. (x 390). A, front view ; B, transverse section of stem, showing 

 side view ; C, siliceous residuum after maceration. (After de Barj-.) 



internode itself, from above downwards. At the angle where the two 

 arms meet, the formation of tracheides begins in each ; the lower end 

 of each bundle unites by two lateral branches with the two next bundles, 

 one on each side, of the next lower internode ; and the bundles are 

 therefore of the description known as ' common.' Their course re- 

 sembles more that of the bundles of most Dicotyledons and Conifers 

 than that of ferns. Each bundle is traversed longitudinally on its axial 

 side by a carinal canal, occupying the place of the first tracheides, 

 which have become absorbed ; right and left of this, in the mature 

 bundle, are reticulate, annular, and scalariform tracheides ; on the 

 outside is the phloem-portion of the bundle, consisting of a few wide 



