392 Watson . — On Mesostrobus , a Nezv Genus of 
Appendix, written February 19, 1909. 
Since the above account of the affinities of Spencerites was written, 
I have seen Dr. Langs paper dealing with the same subject published 
in the Proceedings of the Royal Society of Edinburgh, vol. xxviii, p. 356. 
Dr. Lang discusses the morphology of the cone of Lycopodium cernimm, 
and points out that, after the disappearance of certain mucilaginous areas, 
the radial section of a sporophyll resembles that of Spencerites insignis : he 
therefore concludes that the Spencerites sporophyll, as we know it, is only 
the remnant of a much larger mass of tissue, much of which has broken 
down into mucilage, and that there is some genetic connexion between the 
two species. 
Dr. Lang shows that in the cone of Lycopodium cernuum the sporo- 
phylls, which are arranged in alternating verticils, are connected with one 
another, and brings forward certain evidence to show that in some cases the 
distal parts of the sporophylls of Spencerites insignis may be confluent, and 
from this draws the conclusion that their proximal parts must have formerly 
had a similar connexion. 
Lang concludes that the outgrowth which actually bears the sporangium 
in Spencerites is of no morphological importance, a view which it will 
be noticed is in agreement with my own. 
He also denies any justification for the view that the portion of 
the sporophyll between the insertion of the sporangium and the axis 
is of axial nature. 
He states that in Lycopodium cernuum this region appears late in 
ontogeny. The theory of the development of Lepidostrobus and Spencerites ? 
outlined above, requires this very region to elongate comparatively late 
in the phylogeny of those genera. The comparison between the observed 
fact of its late appearance in ontogeny in Lycopodium cernuum , of which 
I was formerly unaware, and the assumed late appearance in phylogeny 
of the same region in Lepidostrobus , seems to add considerably to the 
probability of my explanation of the origin of that genus. 
1. The whole weight of Lang’s conclusion with regard to the affinities of 
Spencerites rests entirely on a detailed comparison of certain points in the 
anatomy of one recent species with a Carboniferous species of a very distinct 
genus. 
It is, I think, obvious that comparison of two more or less promis- 
cuously picked species of different genera is far from satisfactory evidence 
from which to draw important conclusions, even if the species are of the 
same age ; if, as in this case, their relative ages are immensely different the 
method becomes even more risky. It is unfortunate that the use of this 
method appears to be on the increase amongst botanists. 
3 . Comparison of Fig. 1 of Dr. Lang’s paper with my Text-figures 
