334 
PROFESSOR W. WILLIAMSON ON THE ORGANIZATION 
Coemans and Kickx, in tlieir ‘ Monographie des Sphenophyllums d’Europe,’* * * § define 
these plants as “ foliis cu neatis, sessilibns, verticillatis, nervo medio destitutis, nervnlis 
autem sequalibus, dichotomis. ” Here again we have an obvious distinction between 
a clear definition and my plants. The circle of areolae in my fig. 27 clearly mark 
the positions of a verticil of median leaf bundles, whilst the leaves m and m in 
that figure as clearly show that but one such leaf-bundle went to each leaf, hence 
we have here no dichotomization. Had these nervnres branched we should have 
found that of 24, m, doing so long before it had advanced so far into the leaf. Con- 
necting this with the fact that none of my other sections show a trace of such 
multiplied nervures as are seen in those of Sphe nophyll urn Stephanense, figured 
by M. Renault,! I still conclude that my examples are true Aster ophyllites. It 
is true that M. Grand -’Eury recognizes a group of Sphenopliylla, “ ou les feuilles, 
en nombre variable des tiges aux branches, ont un seule nervure radicale et corre- 
spondant sur la tige a autant des petites cotes. But the plants which he places 
in this group are only the several varieties of the well-known and well-marked species, 
Sphenophyllum Schlotheimi and august folium. That my plants do not belong to 
this group is obvious enough, yet those composing it are the only ones which, like 
mine, have the “nervure radicale unique.” Even were it otherwise the number of 
the leaf bundles in my specimens are very far from being “ correspondant sur la 
tige a autant des petites cotes.” I see no reason therefore for abandoning my original 
conclusion that my plants are true Aster ophyllites, and that Aster ophyllites and 
Sphenophyllum are genera so closely allied that their separate existence finds but 
little justification in nature. 
Before leaving the subject of As ter ophyllites, I may express my surprise that 
Mr. Carruthers, in a recent article § reiterates his belief in the occurrence of elaters 
in connection with the spores of Calamostachys Binneana, notwithstanding my clear 
demonstration in my fifth memoir, that they do not exist. Mr. Carruthers implies 
by this reiteration his continued belief in the Calamitian character of these fruits ; 
whereas the very remarkable difference in the structure of the cellulo -vascular axes of 
the two plants renders it absolutely impossible that such can have been the case. I 
need only quote the late Dr. PiOBERt Brown’s estimate of the value of such differences. 
“ To the argument derived from an agreement in structure between axis of stem and 
strobilus I attach considerable importance, an equal agreement existing both in recent 
and fossil Conifera.”|| 
It is curious that both M. Grand -’Eury and Dr. Dawson have fallen into the 
accidental error of making me regard the Calamostachys Binneana as belonging to 
* Bulletins de l’Academie Royale de Belgique, 2 me serie, tome xvii. p. 138. 
f Aunales des Sciences Nat., 5 me serie, Bot. tom. 18, plate 4, figs. 3 and 4. 
+ Loc. cit., p. 49. 
§ ‘ Contemporary Review,’ February, 1877. 
|| “ Some Account of Triplosporites, an undescribed Fossil Fruit,” Trans. Linn. Soc., vol. xx. p. 471. 
