52 Lee,— The Morphology of Leaf -fall, 
diate cause of leaf-fall lay in the resorption of cells situated between the dead 
leaf and the living tissue of the leaf-base and belonging to the latter. He 
was generally supported by Vaucher (1821), Karl Schultz (1823), de Can- 
dolle (1827), Christian Treviranus (1835), and in part by Van Tieghem and 
Guignard (1882). But the great advance was made in i860 by von Mohl, 
who, although foreshadowed to a certain extent by Schacht (1859), showed 
conclusively that in connexion with leaf-fall two sets of phenomena are 
brought into operation, viz. those connected with the separation of the leaf 
from the stem, and those which lead to the protection of the exposed sur- 
face. Since the publication of his classical paper on the subject the labours 
of a long list of observers have resulted in a general confirmation of his 
results as well as in a great extension of the problem. The extent of our 
knowledge of leaf-fall phenomena in ferns was well summarized by Paul 
Basecke in 1908. The chief workers on Monocotyledonous plants have 
been F. V. Bretfeld (1879) and Fouilloy (1899), while Parkin (1898) and 
Woodhead (1906) have each added observations on the occurrence of leaf- 
fail in various geophilous species of Monocotyledons. In Dicotyledons, 
while many investigators have added to our knowledge of the subject, 
undoubtedly the most important contribution since the time of von Mohl is 
a paper by Tison (1900) in which are published observations on upwards of 
eighty species of plants. Much of Tison’s work had been confirmed during 
the present research before his paper became known to the present writer, 
but a few points of difference will be noted in the separate descriptions 
of the species. Relying on various small differences, Tison describes no 
less than eleven special examples, each of which he makes the type of 
a separate class. Apart from the fact that the creation of so many classes 
is undesirable as rendering the subject unwieldy, it will be shown later that 
such a classification is hardly necessary, but also may result in the separation 
of species which really belong to the same type. 
A description of the phenomena as they occur in the different plants 
studied will now be given. As far as possible common plants will be taken 
as types, and these will be fully described and will be followed by concise 
descriptions of plants which naturally fall into the same class. For the bulk 
of the material and for much assistance I am indebted to Mr. Hales, 
Curator of the Physic Garden, Chelsea. The rest of the material was 
obtained through the kindness of Mr. M. Wilson, B.Sc., Mr. L. A. Boodle, 
F.L.S., and Mr. A. W. Hill, M.A., to whom I beg to express my sincere 
thanks. 
Class I (a). Castanea sativa, Mill. 
As an example of the simple type of leaf-fail, the Sweet Chestnut will 
now be described. It is to be understood, however, that its position in the 
scheme is not to be taken as an indication that it represents the first stage 
