PTERIDOPHYTES—FILICALES 
259 
Roots of tree ferns are sometimes available in greenhouses. In 
some species the stem is covered by a dense felt of small roots, some 
of which will be white and soft at the tip. These roots are likely to 
have about the diameter of onion root-tips, and the beauty of prepara¬ 
tions made from them could hardly be excelled. In the tropics, where 
the plants are often in the 
spray of cataracts and the 
lower part of the trunk is often 
washed by mountain streams, 
a thousand tips might be se¬ 
cured from a single specimen. 
The older roots of Botrych- 
ium, especially the large fleshy 
roots of B. obliquum, cut very 
easily and show a simple exarch 
protostele with 4 or 5 proto- 
xylem points. 
The roots of Angiopteris 
and Marattia, which become as 
large as a lead pencil, may be 
secured in some greenhouses. 
They cut easily after fixing in 
formalin alcohol and furnish a 
fine example of the exarch pro¬ 
tostele, common to all roots 
(Figs. 84 and 85). 
The structure of the leaf will 
appear in sections cut to show 
the sporangia. 
The Sporangia. —To illus¬ 
trate the character of the an¬ 
nulus, select sporangia which are just beginning to turn brown. Fix 
in formalin alcohol and dehydrate as if for paraffin sections; after the 
absolute alcohol, transfer to 10 per cent Venetian turpentine. Stain¬ 
ing is neither necessary nor desirable. 
The various relations of sorus and indusium are best illustrated 
by rather thick sections (10 to 20 y) of material in which the oldest 
sporangia have barely reached the spore stage. Fix in formalin 
alcohol and stain in safranin and anilin blue. 
Fig. 85.— Angiopteris evecta: photomicrograph 
showing a detail of the stele shown in Figure 84. 
Stained in safranin. Eastman Commercial Ortho 
film, Wratten E (orange) filter; Bausch and Lomb 
8-mm. objective, N.A. .50; exposure, lj seconds. 
Negative by Dr. P. J. Sedgwick. X60. 
