1908] GATES—REDUCTION IN OENOTHERA 19 
POLLEN DEGENERATION 
The general question of pollen degeneration in Oenothera is an 
interesting one. It reaches its extreme expression in O. lata, which 
is usually completely sterile in this regard, and in which I have 
already shown (11) that irregularities occur during the reduction 
divisions similar to those found in sterile hybrids. The question of 
sterility is evidently, as TIsSCcHLER (32) suggests, a relative one. 
In O. rubrinervis one is led from a gross examination to judge 
that the pollen production is copious and probably equal to that of 
O. Lamarckiana itself, but in reality many of the pollen mother cells 
fail to complete their divisions. From an examination of sections of 
anthers of O. rubrinervis it is found that in some loculi a large number 
or perhaps nearly all the mother cells may be degenerating in the 
synapsis stage. Frequently the cells are flattened and distorted, 
appearing pressed together for lack of space in the loculus. The 
chromatic contents of such cells often form a dense irregular mass, or 
their nuclei may be in normal synapsis or mitosis, notwithstanding the 
distorted shape of the cell; while still other cells of the same loculus 
may be entirely normal. Even earlier, in the archesporial stage, the. 
tapetal cells in many sections were found to be breaking down, as in 
0. lata (11). No indications of degeneration have yet been observed 
in mother cells of O. Lamarckiana, and very few in the tapetum. 
The percentage of mother cells which thus degenerate in O. 
rubrinervis was not determined. ‘TISCHLER (32) suggests that the 
Causes of sterility in mutants are the same as those in hybrids and in 
plants under cultivation. This general cause he designates as a 
disturbance or derangement of the constitution of the idioplasm, which 
he thinks has taken place in the production of mutants as well as in 
hybrids and under the conditions of cultivation. 
PROTOPLASMIC CONNECTIONS 
. S an interesting fact that large and rather conspicuous proto- 
plasmic connections are found between the pollen mother cells in 
O. rubrinervis, They are usually quite easily seen and it is probable 
that they are always present. They consist of delicate strings or 
rates of cytoplasm connecting adjacent mother cells. In size they 
"Y Steatly, from the delicacy of a spindle fiber to a coarse thread or 
