220 Farmer and Reeves. — On the Occurrence of 
in strong spirit, which, so far as the present plant is con- 
cerned, we find to give results in no way inferior to those 
obtained by the use of absolute alcohol. The sporogonia, 
with their contained spores, were embedded in paraffin, and 
cut with the microtome in the usual way. For staining pur- 
poses we employed a considerable variety of reagents, but we 
obtained the best results after using the following double 
stains ; — gentian violet and orange G., gentian violet and eosin, 
aniline blue and acid fuchsin. In every instance we used 
the stains successively, and on the whole the second of the 
above combinations gave the most satisfactory preparations. 
It should be noted, however, that in dealing with these struc- 
tures, we find it by no means follows that a given treatment 
which may answer admirably for one plant, will succeed 
equally well in the case of another, and in this we are in 
accord with the experience of those who have devoted atten- 
tion to animal centrosomes. The reason of the difference is 
probably to be sought in the slight chemical or physical 
differences which exist between the protoplasmic structures 
in different organisms, but our knowledge of the intimate 
constitution of these bodies is at present so scanty that we 
are compelled to have recourse to empirical experiment, in 
order to determine which reagent may be the best to use in 
each particular case. 
The spores of Pellia epiphylla are crowded with starch- 
grains, and contain, as has been already said, a nucleus of 
considerable size, in which the chromatin occurs in a condition 
of aggregation during the resting stage. The nuclear mem- 
brane is extremely sharply defined, and within the body of 
the nucleus a nucleolus may be seen, though it is not always 
easy to distinguish. 
When nuclear division is about to take place, two structures 
of a minute size appear on the outside of, and in contact with, 
the nuclear wall, and from them beautiful radiations extend. 
These bodies, or centrospheres, are commonly seen to be 
diametrically opposite to each other in position, for we have 
not succeeded in demonstrating them in the perfectly resting 
