18 THE SPHAGNACEZ OR PEAT-MOSSES OF 
properly some care is requisite, for the transverse sections must be 
very thin and examined in water by a good light. We thus find 
four modifications of the position of the chlorophyllose cells :— 
ist. They may lie midway between the anterior and posterior 
surfaces of the leaf, being entirely enclosed by the hyaline 
cells, and the section shows that they are lenticularly 
compressed. 
2nd. They may emerge between the hyaline on the anterior or 
ventral surface of the leaf, their section being triangular, 
so that they resemble a cushion or wedge pushed in 
between each pair of hyaline cells. 
3rd. They may occupy the same position on the posterior or 
dorsal surface. 
4th, They may emerge both in front and back—a condition 
observed only in a few species, and in this case their 
section is circular or oval. 
The hyaline cells are more or less united by their adjacent walls, 
and where they are applied to the chlorophyllose cells the walls of 
the two become grown together; in some species this combined 
wall, as seen from the interior of a hyaline cell, is covered over 
with minute deposits which take the form of papilla, bars, or 
crests, and by some authors have been erroneously described as 
remains of spiral fibres ; these are beautifully seen in our S. Austinz 
and papzllosum, and in the foreign S. Portoricense and Herminiert. 
The hyaline cells nearly always contain threads attached to 
their internal walls, and these threads may form complete spirals 
composed of one or several fibres, or they may be broken up into 
rings, and fragments sometimes run across diagonally so as to unite 
two spirals; they are firmly and intimately united to the inner wall 
of the cells, and often, e. g. in S. sudsecundum, tightly lace up and 
contract the cells at each turn of the thread, probably by contrac- 
tion soon after its deposition. 
The fibrils are not always present in all the leaves; thus in 
S. fimbriatum they are wanting in both the stem and perichetial 
leaves, and some have them in one half of a stem leaf, as S. 
cuspidatum, where they are found in the upper part, but in 
S. macrophyllum no threads are found in any part of the plant. 
By some authors the presence or absence of threads in the cells 
of the stem leaves has been looked upon as of specific value, but 
a study of the varieties of the common species S. acutifolium and 
