50 Leaf Character in Reverted Black Currants 
the leaf (Fig. 23). These veins run to the five main points of the leaf, 
A-E. Now if the submain veins arising from the midrib on one side 
and running to points on the margin (neglecting, of course, to count the 
main veins to B and D) be counted, it will be found that they number 
at least five in a normal leaf. Sometimes there are six or seven, but never 
less than five. In a definitely reverted leaf, however, they are less than 
five, three being a common number in well-developed cases (Figs. 22a, 
28, 29) and in extreme cases they may be reduced to zero (Fig. 46, right- 
hand side). The second character to observe is the margin. In normal 
leaves (Figs. 23, 40) there are numerous fine serrations, many of which 
do not receive any submain branches, but are innervated from branches 
of a lower order. In reverted leaves the margin has comparatively few 
and coarse serrations (Figs. 27-29) and only a few fine serrations exist 
which receive veins of a lower order than submain. 
These two numerical indices have been found extremely useful both 
in the laboratory and in the field for exact work and immediately reveal 
the fact that reverted leaves are sometimes large and broad (Fig. 36), 
small and broad (Fig. 22a), or entirely irregular and deformed (Fig. 31). 
It also shows up the fact that small and comparatively pointed leaves 
need not necessarily be reverted (Figs. 2, 20). 
TEMPORARY REVERSION. 
Using these two methods it has been possible to study certain cases 
of what may be properly called "temporary reversion" which have come 
under the writer's experience. 
Case 1. This case occurred in a pot plant kept in a greenhouse. The 
plant was an oldish one and in poor condition. It possessed two shoots 
A and B, both of which were made up of two or three years' growth. 
The two and three year old wood was bare of buds and of the usual 
blackish colour common to old black currants. Each also possessed about 
nine inches of one year old wood covered normally with buds. 
In early spring the shoot A was ringed just below the one year wood. 
The operation was performed in the usual way, a ring of tissue about 
three-sixteenths of an inch wide as far as the cambium being removed. 
This operation was performed for an object quite apart from reversion, 
but it produced a very interesting effect. As usual the buds below the 
ring, in this case dormant ones, were forced into growth, but the leaves 
instead of being normal were reverted as judged by the venation and 
margin tests. They were not particularly narrow in shape but had a 
generally reverted appearance. The other shoot B did not break from 
