Fuly 30, 1885] 
able to be a mere case of mimicry between a cryptogam 
and a gymnosperm. Our authors, however, lay stress on 
the fact that there are two very distinct types of articu- 
lated root, belonging respectively to the two genera in 
question, but although Prof, Williamson recognises them 
both, he does not specially comment on the fact. As to 
matters of fact relating to the structure of the Calamo- 
dendron stem, opinion does not differ, but the Professor, 
as in the case of Sigillaria, views them as Cryptogams of 
exogenous growth, without, however, admitting the close 
relationship to the Equisetacee advocated by Mr. 
Carruthers. 
The stems of Calamodendron were filled in solid with 
pith or cellular parenchyma when young, but became 
hollow with age, the fistular interior of the stem consisting 
then of a linear series of oblong chambers, making an 
entire internode and separated from each other by trans- 
verse medullary diaphragms. The exogenous zone con- 
sisted of numerous woody wedges separated from each 
other by peculiar prolongations of the pith, to which 
Prof, Williamson assigns the name of primary medullary 
rays, while secondary medullary rays separated the con- 
stituent vascular lamine of each wedge as in recent 
Exogens. These extended vertically from node to node, 
when they underwent a change. The apex or inner face 
of each wedge originates in a duct ‘or canal. Investing 
this woody zone was a thick cellular cortical layer without 
vessels, The bark is very rarely preserved and is not 
exogenous in character, the tripartite division of existing 
Coniferze not being present. The outer surface appears 
to have been smooth, and not fluted longitudinally, at the 
same time masking the articulations. Camalodendron 
thus possessed exogenous wood playing exactly the same 
yéle as in Sigillaria, surrounding the pith, and closely 
resembling the first year’s shoot of a recent conifer ; but 
it differed in the verticellate arrangement of its appendicu- 
lar organs. The structure of the root hardly differs from 
that of the stem, this indicating, according to the authors, 
a peculiarly primitive type, and the rootlets grew from the 
nodes and were branching. Prof. Williamson states, on 
the other hand, that the root is adventitious and not a 
prolongation of the main axis. The leaves or branchlets 
were distributed on the trunk at regular distances on the 
line of the nodes, which were pretty close together, 
alternating regularly from one to another, so that the 
appearance resulting was that of a quincuncial arrange- 
ment, the more obvious on account of the concealment of 
the nodes by the bark. There is no direct proof, but the 
authors believe that the foliage known as Archzeocolamites 
and Bornia, consisting of repeatedly dichotomosing acic- 
ular leaves arranged in verticels around nodes on slightly 
striated stems, really belongs to Calamodendron, in which 
case the male inflorescence was born in catkins some- 
thing like those of the Taxez. Sir J. Dawson, however, 
states that he has found leaves like those of Asterophyl- 
lites attached to stems of Calamodendron. The fruiting 
organs are still very imperfectly known, but Prof. William- 
son believes them to have been a heterosporous Strobilus 
like those of Lepidodendron. The authors, in conclusion, 
remark upon the resemblance between leaves of Bornia 
and those of Trichopitys and Bryon, which are true Salis- 
buriez, for, though the one is verticellate and the other 
spiral in disposition, the possibility of an easy transition 
NATURE 
2... ea ae 
291 
from one to the other is exemplified in Calamodendron, 
and both modes occur together in existing Cupressinez 
and the young Abietinez. 
Prof. Williamson believes that Calamites and Camalo- 
dendron are one and the same plant, and this a cryptogam. 
Against the exogenous wood he sets the cryptogamic bark, 
the Strobilus with Calamite structure full of spores, the 
adventitious roots and the verticellate arrangement of the 
leaves. It seems hardly possible, however, that such 
observers as A. Brongniart, M. Grand’-Eury, M. Rénault » 
and our authors canall be mistaken. In the former volume 
a graphic description was given of the growth of the 
Equisetum-like Calamites as they occur at St. Etienne. 
Prof. Williamson has not come across an undoubted 
Calamite, and very prudently disbelieves in their exist- 
ence, but his evidence seems negative rather than positive, 
and we have already seen in several instances that coal- 
plants may have flourished in great numbers in one 
country and yet be exceedingly rare in another. The 
Carboniferous lasted over an immense period of time, 
and there appears less reason, as their plants become 
more completely known, to suppose that the forests were 
then composed of few types universally distributed. 
Development was proceeding actively, and it is quite 
conceivable that a gigantic primeval Cryptogam might 
take on phanerogamous characters without greatly modi- 
fying its external appearance. 
Another remarkable cryptogam with exogenous wood is 
described by Prof. Williamson as Astromyelon. The 
stem was hollow, and except that it was not articulated, 
resembled that of Camalodendron. It appears that the stem 
and branches grew together under exactly the same relation 
as those observable in an ordinary exogenous tree, the 
latter not differing materially in their outward appearance 
from those of an ordinary pine. He appears to have felt 
hesitation in classing it, as he uses the expression “Tam 
inclined to place” it among Cryptogams. Its affinities he 
considers to be with Marsilea, and we have thus—perhaps 
—in the coal-measures arborescent representatives of the 
Lycopodiaceze in Lepidodendron, of Equisetaceze in 
Camalodendron, and of Marsiliaceze in Astromyelon, all 
of them having possessed rudimentary exogencus trunks. 
J. STARKIE GARDNER 
HARBOURS AND DOCKS 
Harbours and Docks. By L. F. Vernon-Harcourt, M.A. 
(Oxford ; Clarendon Press, 1885.) 
N the author’s previous work on “ Rivers and Canals ” 
I the science of hydraulic engineering received a valu- 
able addition and the subject was treated, as far as it was 
necessary for inland works, in a masterly manner, fully 
upholding the author's high standing in his profession. 
We have now another work by the same author, in which 
the sequel to “ Rivers and Canals” is given. In “Harbours 
and Docks,” sea-works and kindred engineering subjects 
receive full consideration, the two books containing to- 
gether an excellent collection of data on hydraulic 
engineering generally. 
Of all the many branches of the engineering profession, 
that of hydraulic engineering pertaining to sea works and 
similar constructions trusts less to theory and more by far 
to practice than any other. The hydraulic engineer for 
