192 
The Ohio Naturalist. 
[Vol. IV, No. 8, 
THE JACKET LAYER IN SASSAFRAS. 
John II. Schaffner. 
In the ovules of some angiosperms a definite nutritive tissue 
invests the einbryo-.sac, while in others no such layer exists. 
This nutritive jacket appears in all cases to be simpl}’ a modifica- 
tion of one or more layers of cells on the inner wall of the ovule. 
It is purely a phj’siological tissue and is usually described as 
consisting of cells with deeply-staining contents. It is much less 
definite in structure than the tapetum in the microsporangia of 
the stamen, but reminds one of the so-called spongy tissue in the 
ovule of the pines and related jilants. Although usually described 
as a dark staining tissue, there are examples where just the 
opposite is the case. Cook ( 1 ) describes the tissue in the wall of 
the ovule of Agrostemma githago as consisting of two zones, the 
inner zone consisting of thin-walled cells which degenerate while 
the embryo-sac is enlarging. Although the cell walls of the zone 
were very delicate, the entire layer was sharply separated from 
the outer tissue by a very thick limiting wall. 
Fig. I. Ovule of Sassafras, showing jacket layer, a, cross section ; b, 
longitudinal section. 
While studying some preparations of Sas.safras sassafras, the 
writer observed a jacket of cells surrounding the mature embryo- 
sac. This layer shows some resemblance to the delicate zone in 
Agrostemma, but there is no distinct limiting wall on the outside. 
It is from one to several layers of cells in thickness and the cells are 
light-colored with Delafield’s haematoxylin and Heidenhain’s 
haematoxylin, while the cells of the outer zone stain very dark 
(Fig. I , a, b). The cells have large vacuoles and comparatively little 
