Histology of Monocotyledons. 1 5 3 
five irregular layers of small narrow cells result from the 
activity. 
In these plants, besides the perfect foliage-leaves, there are 
sheathing phyllome-structures external to them, the lower 
parts of which also swell to form reserve bulb-scales, while the 
upper parts remain membranous and afford a covering to the 
active region of growth in the young foliage leaves. These 
upper sheathing parts are likewise divided off from their 
lower reserve-storing portions by the formation of absciss- 
layers. These in the case of Galanthus nivalis are well formed 
by the end of March, that is some time before those of the 
foliage-leaves. 
The plane of detachment is through the middle of the 
absciss-layer, and previously to the separation the walls of 
the newly-formed cells become suberised, giving a deep yellow 
coloration with iodine and sulphuric acid, whereas the other 
cell-walls stain blue. 
The plants in which these absciss-layers have been noticed 
by me are Narcissus P seudo-narcissus and N. poeticus , Galan- 
thus nivalis , Leucojum vernum and L. aestivum. No doubt 
other species of these genera exhibit them, and most likely 
other bulbous Amaryllideae. 
Such an absciss-layer, by means of the corky walls formed 
and by the closure of the vessels, may possibly be a protection 
against the entrance of Bacteria or fungus-hyphae into the 
scales, and also a check to the passage of water out 
of them. 
Botanical Laboratory, Cambridge. 
M % 
3 
