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Blackburn. — On the Vascular Anatomy of 
different directions in the various species showing that peculiarity. An 
interesting form is to be found in Anemone apennina and E rant his hie mails. 
Near the periphery of the tuber is a ring of bundles of plumular origin, 
in the latter case connected by a well-marked cambium. The cotyledonary 
traces and some plumular tissue (in A. apennina) form a quite separate 
medullary system. These two groups of vascular tissue join at the base of 
the tuber. 
The other anatomical variations are not so directly correlated with the 
morphology. 
(d) The number of strands contributed by each leaf, though pre- 
vailingly three, is not always so. The first foliage leaf of Paeonia arborea has 
five traces at its base, whereas quite frequently, in Anemone sylvestris and 
many other seedlings, the strands of the first and sometimes more leaves 
are reduced to one at the point of insertion. This may be compared with 
the one double bundle found in the cotyledons, and is probably directly 
correlated with a reduction in the size of the leaf. 
(e) The age at which cambial growth first appears is another feature 
which varies greatly. In Nigella hispanica , an annual form, it is first seen 
at a very late date and does not show great activity, whereas in Aconitum 
Wilsonii the very small amount of primary xylem in the bundles is scarcely 
differentiated before a complete ring of cambium is present (see Text-fig. 7). 
It seems possible that the date of appearance of the cambium may be 
directly correlated with the amount of primary tissue in the bundles. 
(f) The most conspicuous exception to the general type of seedling 
anatomy is that found in the genera Ranunculus , Trollius , and Caltha. 
This is described by Professor Jeffrey 1 in the genus Ranunculus and in the 
young rhizomes of Anemone pennsylvanica. It consists of a tubular stele 
interrupted by leaf-gaps and bounded both internally and externally by 
a more or less well-marked endodermis, which may, however, be quite 
absent. The evidence brought forward in this paper suggests that the 
tubular nature of the stele may be a secondary phenomenon. The signi- 
ficance of the internal endodermis will be discussed later. 
Thus, with a few exceptions, the structure of the seedling, both as 
regards morphology and anatomy, is constant throughout the group, 
whereas there is considerable diversity in the adult, and this diversity may 
be found in forms whose seedlings show great similarity, 
A consideration of the three genera Aquilegia , Thalictrum , and 
Anemone , serves to illustrate this point. With the exception of the two 
tuberous species of Anemone, all the seedlings of these genera that have 
been examined show a remarkable anatomical resemblance to one another, 
even in histological details, while there are marked differences in the adult 
anatomy. 
1 Jeffrey: loc. cit., pp. 615-20. 
