500 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
respecting the small size of the aerial branches lead to some practical suggestions. If 
they prove to be of universal application, they leave us in no doubt as to which are 
aerial and which subterranean branches. Wherever a branch has had a diameter equal 
to that of several of the woody wedges combined, it appears to have been a subterranean 
one. The aerial ones, on the other hand, have rarely, if ever, had a diameter, apart from 
their yet unknown cortical investments, exceeding that of two woody wedges. This con- 
clusion agrees with what we see on the indisputably aerial stems of ordinary Calamites. 
I have already observed that, in such, the concave depressions, indicating the points from 
which branches have fallen, are very small. The form of these concavities, allowing for 
the effect of surface-pressure, corresponds exactly with that of the base of the specimen 
now described. The exceeding rarity of fossil stems to which branches remain attached, 
at least in British strata, indicates that the connexion between the two has been very 
slight. The conical base of the twig imbedded in the woody zone has been united with 
the vessels of the latter throughout its entire surface ; but the suddenness with which the 
vessels have been deflected from a vertical to a horizontal course may have been a source 
of weakness, and led to the almost habitual disarticulation of the branches. These ap- 
pear to have been detached as easily as the leafy shoot is screwed out of the top of a 
pine-apple, leaving, in like manner, conical cavities behind them impressed upon the 
casts of the pith. 
I do not propose to enter at length in the present memoir into the questions of the 
foliage and fruit of the Calamites. Of the foliage I have not seen sufficient to enable 
me to balance the discrepant testimony of the writers who have preceded me. My indefa- 
tigable friend, Dr. Dawson, of Montreal, thinks he is able to distinguish the leaves of 
Calamites from those of the fern-like Aster ojphyllites. M. Grand’ Eury regards the 
Asterophyllites as belonging to stems that have but a vague and distant resemblance 
to those of Calamites. Mr. Carruthers is inclined to believe that Asterophyllites , 
Annularia , and Sjyhenophyllum are but modified forms of one common genus, and 
that they collectively represent the foliage of Calamites. The structure of the stems 
and branches which I have described exhibit so marked a tendency towards verticil- 
late arrangements, that we should naturally turn to fossil leaves similarly disposed 
in searching for the foliage with which to clothe them. At present, however, our inform- 
ation does not appear to me to be sufficiently definite to enable us to settle the dis- 
puted question. The three genera named are the only ones found in the Coal-mea- 
sures possessing the needful verticillate arrangements, and I have no doubt that we 
must seek the required foliage amongst them, but under what limitations is yet to be 
ascertained. The remarks just made apply with almost equal force to the fructification 
of the Calamites. Several varieties of cones or strobili have been found in the shales 
of the Lancashire measures belonging, or allied to Sternberg’s genus Volhnannia ; but 
these rarely retain their internal structure. Mr. Binney has figured, under the name of 
“ Cone of Calamodendron commune ,” one from ironstone, in which the structure is pre- 
served ; whilst Mr. Carruthers has described and figured the same cone* under the 
* Journal of Botany, December 18G7. 
