362 The Ohio Naturalist. [Vol. XV, No. 1, 



buds were killed in Schaffner's weaker chrom-acetic acid with a 

 trace of osmic acid added, being left in this for twenty-four 

 hours. After being thoroughly washed in water, the material 

 was dehydrated by passing it through the various grades of 

 alcohol to 70%, where it was left until September, when it was 

 passed through the higher grades into chloroform, from which 

 it was gradually passed into pure ]3arafine and imbedded. Sections 

 10/x to 13^1 thick were cut. 



Several methods of staining were used. The first tried 

 was analin safranin, which was a fairly good stain, but it did 

 not make enough differention between the chromatin material 

 and the cytoplasm to be easily studied. Next Heidenhain's 

 iron-alum haemotoxyhn was used and found to be very good, 

 staining the chromatin material black and the surrounding 

 tissues brownish. In using this stain, the slides were passed 

 through turpentine, xylol, the different grades of alcohol to 

 water, then passed into iron-alum, where they were left for two 

 hours; after being well washed in water they were left four hours 

 or longer in Heidenhain's haemotoxylin after which they were 

 washed and placed in iron-alum to clear, and after dehydrated 

 they were mounted in Canada balsam. The most satisfactory 

 stain was Delafield's Haemotoxylin. The slides were passed 

 through the alcohols to 25%, then into Delafield's Haemotoxylin 

 where they were left for two hours, after which they were washed 

 in water and passed up through the alcohols and mounted. 



INVESTIGATION. 



The earliest preparations show the resting cells after the last 

 archesporial division, but before the tapetum has become 

 differentiated. In the youngest sporocytes the nuclei are small, 

 measuring 9^ or 1(3^, and the cells fit closely together forming a 

 compact mass. In many nuclei there are several nucleoli present 

 which do not appear spherical, but have one or more finger-like 

 projections. In the youngest sporocytes the chromatin material 

 seems to be arranged in a loose reticulum (Fig. 1), which is not 

 unifonnly spaced throughout the nuclear cavity, and is easily 

 distinguished in it. Following this reticular stage the chromatin 

 material has a tendency to draw together in masses which are 

 rather definite in shape, spongy and flaky in appearance, and have 

 fine threads radiating in all directions from the central lumps. 

 (Fig. 2). 



There is a tendency for these spongy masses to become more 

 compact and definite in shape, approximating the reduced number 

 of chromosomes, (Fig. 3), and without doubt these are the pro- 

 tochromosomes described by various authors, and designated 

 as "prochromosomes" by Overton and Strasl^urgcr. It is prob- 

 ably at this stage that the univalent chromosom.es are paired in 



