THE EXCHANGE OF MATERIAL BETWEEN NUCLEUS 
AND CYTOPLASM IN PEPEROMIA SINTENISII? 
WILLIAM H. BROWN 
(WITH PLATE XIII) 
In describing the development of the embryo sac of Peperomia 
sintenisii, the writer showed that at the time of the fusion of the 
sexual nuclei globules of cytoplasm were taken into the fusion nucleus. 
This phenomenon was not studied in detail at that time, but seemed to 
be worthy of further study, as it offered the possibility of throwing 
some light on the relation between cytoplasm and nucleoplasm. For 
the investigation of this problem material which had been fixed in 
chromacetic acid was cut 10 m thick and stained with Flemming’s 
triple or Haidenhain’s iron alum-hematoxylin and eosin. 
As the male nucleus of Peperomia sintenisii approaches the egg, 
just before fusion, both nuclei come to have cup-shaped depressions 
in the sides facing each other (figs. 1-5); the other parts of the nuclei, 
however, have a fairly regular shape. The depressions in the two 
nuclei may correspond closely to each other (figs. 2, 3), or they may 
not (figs. 1, 5). The number of depressions is also variable in differ- 
ent nuclei, there being one in each nucleus in figs. 1, 2, two in jig. 3, 
while jigs. 4 and 5, which were taken from the same pair of nuclei, 
show three depressions in each nucleus. When the two nuclei come 
together, the nuclear membranes disappear where the nuclei touch 
each other, but remain intact around the depressions, the cytoplasmic 
contents of which appear as vesicles within the nucleus (figs. 6-18). 
Fig. 6 shows a case in which one vesicle is caught in the nucleus 
while two others are probably in the process of being inclosed. Fig. 
7 shows one vesicle inclosed in the nucleus and another nearly inclosed. 
The number and size of the vesicles, like the depressions giving 
rise to them, are variable (figs. 8-18). When the cytoplasm is first 
inclosed in the vesicle, it takes the usual cytoplasmic stains (jigs. 
7-9), but it gradually stains less and less until the vesicles are dis- 
tinguishable from the clear nuclear sap only by the membranes which 
* Contribution from the Botanical Laboratory of the Johns Hopkins University, 
No. rr. 
189] [Botanical Gazette, vol. 49 
