The Ohio Naturalist. 
[Vol. XIV, No. 1, 
190 
of chromosome formation, one involving a side to side pairing, 
the other an end to end. He finds a continuous spirem and twelve 
chromosomes but makes no mention as to how the chromosomes 
are formed. In O. gigas (5) he notes an irregularity in the way 
homologous chromosomes seem to pair. 
Davis first studied the reduction division in O. grandiflora (1). 
In the early sporocyte he describes chromatin material around the 
periphery connected by delicate strands. These strands thicken 
by what seems to be a process of absorption of the chromatin 
bodies and fill the nucleus with a close reticulum. He calls the 
synizetic contraction synapsis. At the end of the contraction 
stage the spirem has assumed the shape of seven bivalent chromo¬ 
somes some of which, he says are linked together. These rings 
.are later pulled apart on the spindle. 
In his second Oenothera paper on O. biennis (2) he calls the 
dark staining masses found around the periphery of the nucleus 
prochromosomes. He finds no evidence that they are arranged 
in pairs, but says whenever there are two together they lie end to 
end. Later on he finds a spirem out of which is constricted a 
chain of fourteen chromosomes. He speaks of a longitudinal 
split which appeared before the heterotypic chromosomes reach 
the poles. 
The buds of Oenothera biennis which were used as material 
for this study were collected west of Cincinnati during the summer 
of 1912. They were killed in Schaffner’s weaker ehromacetic 
acid and run up through the grades of alcohols to absolute. 
The imbedding was done from chloroform. Sections were cut 
10 microns thick and stained. Both Delafield’s and Heidcnhain’s 
haemotoxylin were used, the Heidenhain’s giving the better 
results. The iron was used for four hours and the stain over 
night. 
In the very young sporocytes (Fig. 1) there is a reticulum on 
which can be seen an indefinite number of chromatin masses or 
granules. A little later (Figs. 2 and 3) this chromatin material 
collects in seven little masses which represent the protochromo¬ 
somes. In some of the sporocytes these protochromosomes 
appear double. Their double nature is more easily studied in 
the preparation than reproduced on paper for the two parts of a 
single protochromosome can often be seen best by focusing. 
The masses are so large that on first sight they might almost be 
taken for the bivalent chromosomes except for the small size of 
the young sporocyte and the condition of the tapetum. The 
tapetum in the younger stages has but one nucleus to each cell 
while in the later phases each tapetal cell has two nuclei. In 
passing from the younger to the older stages the tapetum retreats 
from the sporocyte as the sporocyte increases in size and rounds 
up. The nucleolus is quite distinct and need never be confused 
