284 Reed . — A Study of the Enzyme- secreting Cells in the 
until more plants have been examined. The behaviour of the nuclei in 
Phoenix appears to contradict any assumption which could be made 
concerning Zea. 
The nuclei in the two plants increase in size for a time as germination pro- 
gresses. In Phoenix this increase ceases when the embryo is but a few centi- 
metres long, and the nucleus then appears to become smaller, though it is 
probable that enzyme-formation is greater after the nucleus begins to diminish. 
The nuclei may increase in size merely because the cells increase in size. 
There are also differences in the behaviour of chromatin and nucleoli in 
the nuclei of the two plants. In Zea the nucleoli are large when the activity 
of secretion begins, and diminish in size as it progresses until they are no 
longer visible. The quantity of chromatin, on the other hand, increases as 
the nucleoli diminish. In Phoenix the nucleoli are present in all stages of 
secretory activity, attaining their maximum size about the time the cyto- 
plasmic granules begin to disappear. The chromatin, scanty at all times in 
comparison with Zea> shows slight changes in quantity analogous to those 
occurring in Zea. 
In the secreting cells of Zea the greatest apparent activity was reached 
when the nucleoli had disappeared and the chromatin had greatly increased. 
When the activity ceased, there was a formation of large nucleoli simul- 
taneous with a disappearance of chromatin (Fig. 8). When the activity of 
secreting cells was checked by means of low temperature, it was found that 
the chromatin disappeared and large nucleoli were formed. 
If these facts be interpreted to mean that there is some kind of re- 
lationship existing between the chromatin and nucleolus, such as has been 
postulated by Rosen ('95), Dixon (’99), van Wisselingh (’00), Gardner (’01), 
and others, then the difference between chromatin and nucleolus appears 
to be one of degree rather than of kind. The observations would seem to 
indicate that the material in the form of nucleoli was in a less active 
state than when in the form of chromatin, and as the cell-metabolism 
increased the latent substances became active. 
Our ideas of the relations of the nucleolus to the other constituents of 
the cell are, as yet, entirely hypothetical. There are opportunities for 
studying the nucleolus of secreting-cells which seem capable of yielding 
better results than those hitherto obtained during the process of mitosis, 
because the former are performing their normal metabolism instead of 
being interrupted by the process of division. 
The fact that these cells are both absorbing and secreting organs gives 
added importance to a point raised by Rosenberg (’99) concerning the causes 
for an increase of chromatin during secretory activity. He thought it might 
follow either as the result of the formation of an enzyme or as the result of 
absorbing abundant nutrition. The ease with which the scutellum of Zea 
may be separated from the endosperm suggests an experiment (which, 
