470 Oliver , — The Ovules of the older Gymnosperms. 
outside the foramen, but it was only by the middle of August 
of the second year that these elements could be recognized 
in the actual foramen and continuing to the place of forking. 
A seed freshly picked at this stage and stood with its 
cut base in a watery solution of eosin sucked up the eosin by 
its xylem, and the pigment was drawn right through the 
foramina and a little distance further, i. e. up to the limit 
of differentiation of tracheides. 
It has been stated that the desmogen-strands run right 
across from one foramen to the other, encircling the base 
of the free nucellus, but in the nearly ripe seed they can 
no longer be traced all the way. Running in the hypoderm 
of the nucellus in the angle of the groove between nucellus 
and integument they become merged in the peculiar hypoderm 
of the nucellus which becomes prominent In July. This tissue 
consists of large, thick-walled, mucilaginous, pitted cells of 
remarkable appearance which first arise in the nucellus ad- 
jacent to the trough, but ultimately appear in the downward 
continuation of the nucellus, everywhere enclosing the pro- 
thallium in a continuous sheath or mantle. This layer is 
very characteristic, and its protoplasm becomes filled with 
oily granules. Its actual signification is obscure without 
special investigation, but its appearance suggests that it serves 
in some way as a go-between in respect of food that is being 
transferred from the green assimilating layer of the arillus to 
the prothallium. Perhaps it may be termed provisionally 
a £ digestive layer.’ It is in this layer that the strands from 
the foramina become lost. Indeed as a strand is followed 
from the forking-place the tracheides slowly die out and large 
mucilage cells begin, the impression gained from a study 
of these transition regions being that the mucilage cells and 
tracheides mutually exclude one another — that they are pro- 
duced from identical structures. 
For the completion of this brief account of the vascular 
system of the seed in Torreya one point remains to be added. 
It was stated at p. 468 that only the central portion of the 
reunited bundle turned sharply inwards and traversed the 
