An Example of Leaf-enation in Allium ursinum L. 57 
Theory. The two blades of the abnormal leaf, however, are more 
easily explained as expansions of the apical part of the “ petiole ” 
than as those of the “midrib/’ because the petiole itself is flattened, 
and has three prominent “ribs,” the lateral ones of which are con¬ 
tinued only in one of the blades. Moreover, the continuity of double 
nature in “petiolar” and “laminar” regions would seem to suggest 
that the “petiole” and “lamina” are morphologically the same. 
Summary 
1. In this paper an example of leaf-enation in Allium ursinum 
is recorded for the first time. 
2. The “ doubling ” is found not only in the “ laminar ” but also in 
the “petiolar” region. This seems to be unique, because no example 
of leaf-enation is found to be on record, which is continuous in both 
“petiolar” and “laminar” regions. 
3. There is one series of bundles in each of the blades, but their 
orientation is opposite: thus the sport obeys the “law of laminar 
inversion, according to which opposed laminar surfaces are similarly 
constituted.” This law has been found to hold good by Worsdell 
and others in nearly all the examples of leaf-enations. 
4. The “doubling” is explained as the result ol formation of two 
opposite grooves in the “petiole,” and the development of wings in 
its apical portion by the four ridges thus formed. 
5. An example of leaf-enation is described from Xanthosoma 
appendiculatum , which is also explained as the result of grooving, 
associated with development of wings. It is also suggested that it 
is possible to conceive that the normal blade has also been produced 
in the same way. This is interesting in view of Arber’s description 
of similar methods being employed by Palms and some Irids in the 
formation of “pseudo-laminae.” 
6. This only recorded example of the enation extending down to 
the flattened “petiolar” region, being found in a monocotyledonous 
leaf, indirectly lends support to the view that the “lamina” in 
monocotyledons may be only a modified portion of the petiole. 
In conclusion I have much pleasure in expressing my hearty 
thanks to Prof. Seward and Mrs Arber for their valuable help given 
to me in connection with this paper. To Miss M. G. Campin, of 
Newnham College, Cambridge, I am indebted for many suggestions 
and for drawing the diagrams, which are reproduced in this paper. 
Botany School, 
Cambridge 
