382 
CLIFFORD H. FARR 
Living Cells 
A study of the pollen mother cells of Magnolia tripetala L. was 
begun on April 21, 1 91 7, and continued over the first of May upon 
material collected in the New York Botanical Garden. Before the 
initial date the buds and bud scales remained intact, and the buds 
were not enlarged much over their winter condition. As synapsis 
takes place, however, there is a very rapid increase in size, and the 
outer bud scales tear loose from their basilar attachment but remain 
coherent at their apices forming a sort of "calyptra" over the swelling 
bud. Not all the buds of the tree develop simultaneously. The 
external aspect of the bud in the above-noted particulars seems to 
indicate rather characteristically the exact cytological stage of the 
mother cells within. Just the relation of the swelling of the bud to the 
stages of reduction is not exactly clear. The anther swells more rapidly 
than do the pollen mother cells, so that the latter become suspended 
in the liquid of the pollen sac. 
In living material the spindle fibers are easily discernible in the 
equators of the cells in the heterotypic division and also between the 
sister nuclei of the second mitosis. The fibers extending from the 
furrows to the nuclei are especially prominent. A few cases were 
noted in which an equatorial streak resembling a cell plate was ap- 
parent in the mother cell. In only one case was it found in a cell which 
also appeared to have furrows. 
The usual number of microspores within a single mother-cell wall is 
four; but the occasional occurrence of supernumerary pollen grains 
is noted here as in several other flowering plants, notably Fuchsia (2) 
and Hemerocallis (10). One case was noted in MagnoHa in which 
there were seven cells within the mother-cell wall, but none were found 
with more than this number. In several cases there were four micro- 
spores of normal size and one additional small one, or in some instances 
two such small cells. 
Several stamens were studied with a view to determining the 
various ways in which the four microspores are arranged with respect 
to each other. Quantitative results were also obtained to determine 
the percentage of each type of arrangement. In Table I five types 
of arrangement are recognized. The accompanying drawings show 
the characteristic appearance of each type as seen through the micro- 
scope. Type I is the arrangement referred to by Giesenhagen (7) 
