Structure and Function of Endodermis in Abietinece 271 
VIII. Fresh strong alcoholic solution of chlorophyll. 
Sections immersed in this solution for about half-an-hour in the 
dark show a green coloration in the suberised and cuticularised 
layers. This was not found to be such a good differential stain as 
either alkannin or Sudan III as the green colour does not show up 
against the yellowish background of the leaf so sharply as does the 
red. 
IX. Aqueous solution of caustic potash. 
Cuticularised layers appear a bright yellow colour, suberised 
membranes assume a bright reddish-yellow colour, and lignified walls 
are stained dull brown. The differentiation is intensified by warming 
the sections in potash, and prolonged heat causes the suberised and 
cuticularised layers to decompose and dissolve. 
X. Schultze’s solution. 
Cellulose membranes swell and turn blue, lignocellulose walls 
stain deep brown, and suberised and cuticularised layers yellow- 
brown. 
Useful stains for the differentiation of the walls were found to be: 
I. Alcoholic safranin followed by light green in clove oil. 
II. Alcoholic malachite green followed by eosin in clove oil. 
The text-figures were made from camera lucida drawings and are 
slightly diagrammatic in character. 
Results 
The Abietineae may be considered to include two main groups: 
(1) The Pineae comprising the genera Pinus, Picea, Pseudotsuga 
and Larix. 
(2) The Abieteae comprising the genera Abies, Cedrus, Tsuga and 
Pseudolarix. 
One example of every genus in each of the two groups was 
examined, and in the case of Pinus several species were dealt with. 
The following were among those investigated: 
I. Pinus sylvestris L. 
An endodermis is present in both the very young stem and the 
very young root of the pine seedling, but is absent from all parts of 
the older plant with the exception of the leaves. In the latter, how¬ 
ever, it is always present, its nature varying both with the type of 
leaf and with its age. 
