ome 
rice” |r 
500 MESSRS. R. PAULSON AND S. HASTINGS ON THÉ 
section remained in the Methyl-Violet-Pyronin for 5 minutes, and the 
whole process took about 8 minutes. 
Haidenhain's iron-alum-hematoxylin is a most useful medium especially 
for bringing out the structure of the chloroplast. The so-called pyrenoid 
and the small lateral body already mentioned are remarkably distinct after 
the application of this stain. 
Erythrocin and eyanin, which have been recommended for sections of 
lichens, differentiate the two components, but the reaction is not quite reliable. 
With the best results from this combination the gonidia become blue, 
the so-called pyrenoid dark blue, while the hyphæ take a pinkish-red 
coloration. 
Gonidia were examined, in the first case, in sections cut immediately 
after gathering the specimens. They were either in situ, that is, in the 
normal position among the hyphal threads, or were slightly separated from 
the section while it was temporarily mounted in glycerine and alcohol. 
Under these conditions and after frequent washings of the entire specimen 
in distilled water, a small number of stray alge were sometimes still present, 
but there was no difficulty in deciding which was the true lichen gonidium, 
In the species of lichens enumerated above, the shape and size of the 
gonidium, and the shape and structure of the chloroplast and so-called 
pyrenoid are remarkably uniform. When saying this we do not forget 
that there may be considerable physiological differences in the algal cells as 
stated by Chodat (2) as the results of his culture experiments. Our investi- 
gations respecting the relationship between the alga and the fungus have, 
however, been strictly anatomical. 
Fully developed gonidia of the lichens in question have a diameter ranging 
from 10 to 20 p with an average approximating to 12 p. They are spherical 
except when subject to pressure, which is especially present at the time when 
large numbers of new cells are being rapidly added to the gonidial layer 
(Pl. 21. Phot. 1). The outer surface of the cell-wall is perfectly smooth, 
The chloroplast is large and differs somewhat during the development of the 
cell. In the daughter cell it is generally smooth in outline, but, as the cell 
enlarges, the chloroplast becomes very minutely verrucose. It is seldom 
sufficiently irregular to warrant the term stellate unless this term is 
employed simply to distinguish such a form from the cup or bell-shaped 
chloroplast which is commonly found in members of the Chlorophyce:e. 
Such a well marked. stellate form as that figured by Chodat in the * Mono- 
graphie d'Algues en Culture Pure,’ under Cystococcus Cladonio, Chod., 
have not seen in the gonidia of Cladonia pyaidata when forming 
of the lichen. : 
It is quite clear that the microscopic characters of the chloroplast have not 
been stated with any great degree of definiteness by the older writers, and 
for this reason it has been not without difficulty that a decision could be 
we 
a component 
