CELLS OF EUCOMMIA ULMOIDES, OLIVER. 249 
reached, which may be due either to the nucleus having come to the end of its functional 
power, or, as seems more likely, to the nucleus having been cut off from communication 
with the growing point of the cell by a blocking up of its lumen with caoutchouc. For 
in many cases in which the end-bulb still contained protoplasmie substance, or at least a 
substance staining like protoplasm, but containing also a large amount of caoutchouc 
granules, the thinner portion of the cell behind the end-bulb was entirely filled with 
a solid mass of caoutchouc, between which and the cell-wall I could not demonstrate any 
protoplasm. 
I searched diligently for а nucleus in these end-bulbs, which at first seemed to me 
likely places for additional nuclei, but could in no case discover any. 
Other dilatations occur occasionally in places where growth has been hindered by 
some obstruction, and here, too, a thickening of the cell-wall takes place (fig. 11). It is 
such an irregular growth in which we get a short horizontal extension, that appears as a 
long cell in the transverse section (fig. 7). 
The bulbous dilatations occur in the most striking manner in the teeth of the developing 
leaves, where they may be seen in large numbers, especially after swelling up the ordinary 
tissues with sulphuric acid (fig. 12). Here they are very irregular in appearance, and 
here they would seem to indicate that the growth of the caoutchouc-containing cells had 
become impeded by the slowness of the development of the leaf. Неге, therefore, the 
cells should still be in a growing condition, and yet in many cells the contents are already 
clear, indicating that the caoutchouc has become set into a solid mass. 
In longitudinal section (fig. 13) the bulbs will be seen arching over the end of the 
vessel and terminating but a few cells behind the meristematie cells of the tooth. 
THE CONTENTS OF THE CELLS (fig. 9, а, 0, с, & d). 
During the early stages of growth of the cells above described, the protoplasm 
contains a number of smaller and some very much larger granules (figs. 5 and 9 a). 
These latter and some of the smaller are of the nature of caoutchouc, and can best 
be identified by the intense blue or violet colour which they assume with acidulated 
methyl green. Their solubility in chloroform is another test. These granules appear 
also in many of the cells of the primary phloem, in which no caoutchouc-containing 
cells occur (fig. 9 d). Nor do these phloem cells become stored with caoutchouc, but 
the granules seem to be re-absorbed, for in older internodes of the same shoot no such 
granules are seen. 
In the caoutchouc-containing cells, the large granules become more numerous till 
the cells are densely packed with granules (fig. 9 б), and finally they become welded 
into a solid mass, which at first shows its origin from a granular matrix by numerous 
lines indicating splits and cracks in the contents (fig. 9c). Ultimately, however, the 
contents become quite homogeneous, as mentioned at the commencement of this paper, 
and form elastic threads, which are observed on breaking asunder a bit of bark or a 
leaf. Тһе contents are then drawn out of the cells and show themselves to be very 
