6 ARISAEMA TRIPHYLLUM 
the dividing walls in various intersecting planes. Soon after the 
completion of the second division the spores round off and separate. 
The first division of the pollen spore nucleus does not occur 
until the walls are well formed. The generative cell is isolated 
by the formation of a delicate wall. The second division occurs 
just about the time of germination. The mature pollen spores are 
spherical with an average diameter of 19 microns. Both intine 
and exine are well developed, the latter being quite firm, without 
evident pores, and thickly set with short, slender spines. 
The germination of the pollen spore and the peculiarities of 
the pollen tube have been briefly described by Rowlee (25). In 
the examination of pollen germinated on fresh stigmas, the writer 
has found that the pollen tubes rarely grow straight but tend to 
become twisted or folded, although to a less extent than found by 
Rowlee in the case of spores germinated in an anther cavity. The 
tube winds about among the outer stigmatic hairs, through the 
hollow style, and then among the 
hairs of the inner stigmatic brush 
before reaching a micropyle. 
An interesting point in con- 
nection with the pollen spore for- 
mation is the appearance of wan- 
dering tapetal nuclei, as described 
by Duggar (9) for Symplocarpus 
foetidus. Just at the beginning 
of the second tetrad division, the 
tapetal cells begin to disorganize 
by dissolving their walls. When 
the pollen spores begin to round 
off and separate, nearly all the 
Migrating tapetal nuclei. 
G, a quiescent stage common 
among almost mature pollen spores. 
E, pollen spore drawn for comparison 
Other figures show amoeboid 
forms suggestive of movement. 
the developing spores. 
tapetal cells have lost their walls, 
and the protoplasm and nuclei 
have passed out into the mass of 
spores. The protoplasm appears 
as a nearly homogenous mass, 
with faint vacuoles, surrounding 
The nuclei have enlarged, and become 
rather densely granular, with distinct nucleoli and vacuoles 
