294 
different H. umbellatum forms dealt with above I have thought it well 
to reproduce some series of leaves collected from the cultivated mate- 
rial in October, 1922. No selection has been made in collecting the 
material, but any plant with leaves in good conditions at that time 
has been included in the series. The leaves have then been approxi- 
mately arranged according to their width starting with the broadest 
ones. Three or four leaves of different sizes have been taken from each 
plant, and the numerals at each of the leaf groups on the photographs 
refer to the field numbers of the plants in the tables. These photo- 
graphic reproductions run from figs. 59—73. 
Fig. 58. H. umbellatum. Fı-plants from a cross within the Vitemölle dune type. 
It should not be thought that the points of difference between the 
above discussed H. umbellatum forms are exhausted by the distinctions 
already made and shown. There are marked differences in the ana- 
tomical structure of the leaf in the various forms. The cultivated in- 
land form of the woodlands has generally two, at the most three, layers 
of palisades (fig. 76 a). Cross sections of leaves of the cultivated Sand- 
hammar dune form (list no. 18) generally show four layers of palisades 
(fig. 76 b), and both the dune form from the west coast and the prostrate 
dune form from the eastern coast have generally 3—4 of these layers. 
Leaves of the cultivated cliff forms from the west coast have about 
the same thickness as those of the dune forms, but the cells, even those 
