76 
Marchantiaceze investigated. Unfortunately I have been unable 
to find an account of the details. Of the Marchantiacee Jar- 
chantia has been the subject of a recent work by Kny already 
cited. This latter is especially interesting, as it shows that in its 
development the young thallus follows step by step, precisely the 
same course described in the young fern-prothallium*. First the 
protonemal filament; next oblique walls cutting off a stagle two- 
sided apical cell ; this is then divided by a transverse wall, and the 
inter cell, by longitudinal walls becomes transformed into the row 
of marginal cells that characterizes the growing point of the older 
thallus. 
Owing to their extreme delicacy, it is almost impossible to 
make satisfactory longitudinal sections through fern-prothallia 
without imbedding them. It is no doubt for this reason that no 
satisfactory account of the cell-division in the apex, subsequent to 
the formation of the thickening back of it, has been given. It is 
possible, however to imbed them in paraffine and it is then a 
simple matter to make very thin sections which show every detail 
of structure with perfect clearness. It is then plainly evident that 
the divisions are perfectly regular and referable to a type found 
among the liverworts. 
To prepare the specimens for imbedding 1 per cent. chromic 
acid was used to fix them, and after dehydrating and passing 
gradually into turpentine, they were placed for several hours in 
melted paraffine. Asastain, Bismarck brown was the most satis- 
factory. A solution in 70 per cent. alcohol was used, staining on 
the slide. In this way the young cell-walls are strongly colored 
and the preparations show every detail with the utmost sharpness. 
SPECIAL INVESTIGATIONS. 
Sections were made of the prothallia of Oxoclea sensibilis and 
O. Struthiopteris, as well as a number of undertermined Polypodi- 
acee, and of Osmunda cinnamomea. In all of these a strong 
resemblance was observed. 
In the larger prothallia of the Polypodiacez, so far as ob- 
served, the growing point consists of a row of several cells, 
(Fig. 3, a, a’, a"), each one nearly four-sided as seen in sections 
parallel with the surface of the prothallium. These divide oc- 
* Kny, |, c. pp. 387-389. Fig. xc, 
