360 Hill and de Fraine. — On the Classification of Seed-Leaves . 
‘in arguing from anatomy to morphology in this matter’ is doubtless 
a matter of individual opinion ; it is certainly a classification which is 
remarkable in the fact that it does not break down when applied, and 
further, it may be remarked that anatomy is frequently a very valuable aid 
in determining morphological status. 
Mr. Compton cites Cupressus torulosa Series C, Abies sibirica Series B, 
and Abies amabilis as examples illustrating that the above classification, 
even when restricted solely to the vascular strands, cannot be applied strictly. 
We have referred to our written descriptions of the transition phenomena in 
these plants, and quite fail to see any difficulty whatever in the interpretation 
with regard to the first and last named plant. The instance o i Abies sibirica 
presented some difficulties which are fully considered and met in the paper . 1 
Of the large number of polycotylous Gymnosperm seedlings examined, this 
particular example, Abies sibirica , is one of a very few, if not the only one, 
in which the interpretation of the value of the cotyledons did not assert 
itself obviously. There is much to be said for a classification which is so 
generally applicable; a conception is not, we think, to be condemned 
because one particular example does not at first sight appear to fit. 
In further support of his contention, Mr. Compton cites his observations 
on Phacelia tanacetifolia , 2 No illustrations are given of the vascular 
rearrangements in this plant, but from his account we should say that our 
classification finds considerable support. 
It does not appear necessary to examine in detail all the examples of 
this plant examined by Mr. Compton ; two, however, may be dealt with at 
some little length. 
Hemitricotyl A : In this seedling there was one entire and one bifur- 
cated cotyledon. The vascular bundle of the former gave origin to one pole 
of the diarch root, whilst the two bundles, which did not fuse together before 
entering the hypocotyl, from the deeply forked cotyledon, together formed 
the other pole of the diarch root-structure. The interpretation is clear — 
there were two whole cotyledons, one of which was so deeply split as 
almost to form two half-cotyledons. 
In the case of Tricotyl B there were three cotyledons, the bundles of 
which divided into two and gave rise to a triarch root-structure. At a lower 
level the triarch arrangement became reduced to diarch. Mr. Compton, 
who traces the vascular changes from the root to the seed-leaves, calls this 
the ‘ diarch-triarch * structure. This method of increase in the number of 
protoxylems is not uncommon among tricotyls. It is not ‘the method 
followed by the vascular bundles of so-called subsidiary cotyledons in 
Coniferae as Mr. Compton states. According to our reading of the facts, 
there were no subsidiary cotyledons in this example of Phacelia : there 
1 Hill and de Fraine, loc. cit. , 1909, p. 191. 
2 Loc. cit., p. 81 1. 
