1901] SPORANGIA AND GAMETOPHYTES OF SELAGINELLA 185 
during the time up to the point of saturation. At this time the 
cover was removed from the vessel to facilitate the evaporation 
of the xylol, and harder paraffin added in small quantities at 
intervals. At the end of two or three days the temperature was 
raised to 65° C., and maintained for one week, after which 
time the xylol had evaporated, and the strobili were infil- 
trated with paraffin. 
At first, on the supposition that such protracted exposure 
to reagents and heat would injure the more delicate very young 
sporangia, the tips of strobili were removed, carried through the 
various media in much less time, and subjected to a temperature 
of 50°C. for about ten hours only. Comparisons later showed 
that these precautions were unnecessary, and that the longer 
exposures produced better results, even in the apical cells. More- 
over, having a strobilus cut zm /ofo was of the greatest value in 
interpretation. Further experiments prove that considerable 
latitude in the direction of longer periods of immersion in the 
various fluids are not injurious, but all attempts to hasten results 
by shorter exposure than the period stated above were unfortu- 
nate. By an oversight, at one time the temperature rose in the 
bath three successive nights to 75°C., but with no injurious 
effects. Some difficulty was experienced in imbedding. The 
paraffin was inclined to shrink away from the rough surface of 
the spore wall, which caused the sections to drop out of the 
paraffin ribbon when transferred to the slide. The difficulty was 
overcome by removing the strobili to the imbedding dish from 
the bath, letting them cool off slightly (to about 40° C.), pour- 
ing on paraffin at a temperature of 80° C., then cooling as 
rapidly as possible in ice water. No further trouble was 
experienced and the strobili could be sectioned without diffi- 
culty. 
Stains.—The best stains for the youngest stages of sporan- 
gia are iron haematoxylin (Haidenhain method), and the so- 
called Flemming triple stain—saffranin, gentian-violet, and 
orange G. Frequently gentian-violet and orange G were 
employed without saffranin; for the gametophyte development, 
