282 MR. А. В. HORWOOD ON CALAMITES SCHÜTZEI, AND 
Pl. 27. fig. 30 represents a few of the ridges and furrows of the latter 
enlarged about three diameters. Some of them are much thicker at one end 
than at the other, whilst there are few in which the two sides are quite 
parallel. But beside this peculiarity the internode itself is unlike its neigh- 
bours, being only about half their length. Were this all, the internode 
might be regarded as ап accidental anomaly ; but when phenomena appear 
in regularly recurring series such an explanation is inapplicable. In 
Mr. Wilde's fine specimen, of which fig. 29 represents a very small portion, 
every eighth internode exhibits these peculiarities. Similar appearances are 
seen in another specimen in the same collection, but here they appear in every 
fifth internode. I have as yet failed to correlate these appearances of the 
medullary cast with any known external features of Calamites, but that they 
have some special significance cannot be doubted. They most probably indicate 
some specific * features of the plant to which they belonged.” 
Thus Williamson, in 1871, anticipates Weiss's characters given to subgener: 
founded in 1876. 16 is a fair inference that we may make, seeing the short 
internode is so repeatedly associated in Calamites, and also in recent Equiseta, 
with branch-bearing internodes, that it has a physiologieal function, viz. : 
to impart strength to the stem. Its position indicates the introduction of a 
new series of organs, since, as we shall see, it follows or precedes the root- 
bearing stem and barren stem, and precedes or follows the branch-bearing 
internodes and strobili. 
When thus considered physiologically, this gradual increase in length of 
internodes (and leaf-sheaths) upwards in living Æquiseta entirely depends upon 
the laws of growth, elongation following cell-growth, with a proper supply 
of water ; and is in accord with general principles. 
And in this connection Strasburger + sums up as follows :— As is often 
observed with the occurrence of many vital phenomena, the rate of distension 
of the walls with the inflation water is not uniform, but begins slowly, increases 
toa maximum rapidly, and then gradually diminishing altogether ceases.” 
П в. Description of specimens of recent Equiseta in which short internodes occur 
as in the extinct Calamarieæ, with proportionally regular increase in length. 
It is an interesting fact, brought out by a study of the fossil forms here 
described, that during the progress of the investigation recent Æquiseta were 
examined and found to possess the same peculiarities as Calamites, in the 
possession of a short internode and a uniform rate of inerease in length. 
Thus characters typical of the subgenus Calamitina occur also in а modified 
form in subterranean stems of Stylocalamites Suckovii (Brongn.), and indica- 
* Present writer's italics. 
T ' Text-book of Botany ' (English Edition), 1903, 
