Mitosis in the Pollen Mother-cells of Acer 
negundo, L., and Staphylea trifolia, L. 
BY 
DAVID M. MOTTIER, 
Professor of Botany in Indiana University. 
With Plates IX and X. 
D URING the past three years the writer has been engaged; with more 
or less interruption, upon the study of the mitotic processes in the 
microspore mother-cells of species of Aceraceae and of Staphylea trifolia , L., 
of the Staphyleaceae, a family closely related to the Maples. In the native 
flora of Indiana, Staphylea trifolia , L., is the sole representative of the family. 
This paper will be confined, however, to the writer’s observations on the 
mitotic phenomena in only one species of the genus Acer and to Staphylea 
trifolia , L., while the results obtained in other Maples will be reserved for 
a future publication. 
In 1909 Darling published the results of a study on the two divisions 
in the microspore mother-cells of Acer negundo , L., but, as will be seen 
from what follows, his conclusions differ widely in certain respects from 
those of the writer. 
Acer negundo, L. 
The resting nucleus. The resting nucleus of the pollen mother-cell at 
the beginning of the growth period reveals the presence of a sparse and 
delicate network upon which are distributed small chromatin granules, 
and a very distinct globular nucleolus. The nucleolus may or may not 
show the presence of vacuoles (Figs. 3, 4). The chromatin granules are 
distinct, and stain definitely both with the triple stain and iron-alum-haema- 
toxylin. The granules vary somewhat in size, and frequently tend to form 
small collections, as may be seen in Fig. 4. In fact, the larger granules are 
usually found to represent aggregates of smaller ones. The majority of 
these chromatin granules are arranged along the nuclear membrane, but 
they occur also upon the linin net which traverses the nuclear cavity. Very 
delicate linin threads frequently extend to the nucleolus, and sometimes 
[Annals of Botany, Vol. XXVIII. No. CIX. January, 1914.] 
