264 Sanford . — Anatomy of the Common 
mass. By about the first of June these spores have fully 
matured, and the spore-masses begin to dry up and decay, 
afterwards falling off from the knot, which also dies and dries 
up, but much more slowly. 
The foregoing general description, based on my own ob- 
servations, agrees substantially with that given by Dr. Farlow 
in the ‘ Gymnosporangia or Cedar- Apples of the United 
States. 5 The following study of the anatomy of the knot 
was made independently, and so far as I am aware the results 
have not been recorded elsewhere. 
That we may more fully understand the changes which take 
place, resulting in the production of the cedar-apple above 
described, it will be necessary first to notice the structure of 
the normal leaf. 
A cross section of the leaf of Juniperus virginiana shows, 
passing from the periphery towards the centre, (1) a distinct 
epidermal system, (2) a layer of rather large parenchymatous 
cells, making up the greater part of the leaf, and (3), near 
the centre, the fibrovascular bundle. The epidermal system 
varies somewhat on the inner and outer surfaces of the leaf. 
On the outer surface is a distinct and quite thick cuticle, 
and beneath this usually about two layers of quite regular 
epidermal cells covering the parenchymatous cells. The epi- 
dermis of the inner surface of the leaf consists of one layer of 
rather large epidermal cells of a more spherical outline. 
Here there are many stomata. 
The parenchymatous tissue is made up of rather large 
ellipsoidal cells loosely packed together, with many inter- 
cellular spaces, and with very definite and somewhat thick 
cellulose walls, in which are often thin places. The cells of 
the parenchymatous tissue, at the time of observation, were 
quite full of starch. 
The vascular bundle is of the collateral type, the xylem 
lying on the side towards the inner surface of the leaf, and 
the phloem towards the outer. The xylem is composed of 
scalariform and reticulated tracheids. 
Turning ‘now to the structure of the cedar-apple, we find 
