An Example of Leaf-enation in Allium ursinum L. 55 
duced by the invagination. I may note here that Willis (1919, p. 692) 
attributes thi^ phenomenon of the formation of the second blade to 
the “ tangential division of the embryonic leaf.” Obviously, I cannot 
accept this explanation. In view of the above explanation of the 
formation, of the second blade, it is possible to conceive that the normal 
blade also is the result of the expansion of the two ridges, which are 
Figs. 6-10. Hypothetical figures to show the various stages in the doubling of 
the “petiole" by the agency of two opposite invaginations. 
produced by a median groove on the upper surface of the apical part 
of the “petiole.” 
Now returning to the abnormal leaf of Allium ursinum, an ex¬ 
amination of Fig. 2 suggests that a process of invagination has been 
at work in it also. Although, unfortunately, I could not secure the 
lower portion of the “ petiole,” yet it seems to me that this apparently 
double nature of the “ petiole ” is due to the production of two grooves 
