I90 The Ohio Naturalist. [Vol. XIV, No. 1, 



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 0. 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 Schafi:ner's weaker chromacetic 

 acid and run up through the grades of alcohols to absolute. 

 The imbedding was done from chlorofomi. Sections were cut 

 10 microns thick and stained. Both Delafield's and Hcidenhain's 

 haemotoxylin were used, the Hcidenhain'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 dou]:)lc. Their double nature is more easily studied in 

 the preparation than reproduced on paper for the two parts of a 

 single protochromosomc 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 

 ta])ctum in the younger stages has but one nucleus to each cell 

 while in the later phases each tapetal cell has two nuclei. In 

 l^assing from the younger to the older stages the tapetum retreats 

 from the sporocyte as the sj^orocyte increases in size and rounds 

 up. The nucleolus is quite distinct and need never be confused 



