EQUISETUMS AND CALAMETES. 87 
that these curious elongated cells external to the cells near the lacuna 
not form a component part of the fibro-vascular bundle. In £. 
of these sclerenchyma cells of Mettenius, which seems to me to indi- 
cate that the so-called bundle in Calamites as described by Prof. 
especially in rh 
20* would be produced. 
ordinary appearance of an Equisetum stem, with the bundles and 
lacuna arranged in the ordinary way; but the sclerenchyma bundles 
are remarkably developed, and run from epidermis to the fibro- 
vascular bun The preparation has been put up in tama Saenae 
in 
The large sclerenchyma band runs from the bundle direct to the epi- 
dermis. No sheath of the fibro-vascular bundle exists, and the pith 
cells internal to the bundles are observed to be slightly selerenchy- 
matous and dark in colour. This is exactly what we find in Calamites, 
the only difference being that in this South American Equisetum the 
sclerenchy ma bundles are separated by the lacune of the cortex, which 
are wanting in Calamites. is 4 
If we consider that outer portion which Prof. Williamson believes to 
natural affinity in adopting the idea of circumferential growth occurring 
in them, 
* Op. cit., plate xxv. 
