TREE FERNS OF NORTH AMERICA—MAXON. ATT 
the blades, but also upon the leaf tissue. In these characters the 
members of the tribe Cyathexw show almost infinite diversity. 
In many species of Cyathea and Alsophila, and less commonly of 
Hemitelia, the trunks are more or less completely covered with 
spines, a fact which no one who has reached out hastily and grasped 
one in a futile effort to stay his rapid descent down some steep, 
slippery, forest-clad slope, is likely to deny. As a rule, however, the 
trunks are spiny simply from the partial persistence of the broken 
stipe bases, which indisputably are spiny. Two stipe bases thus 
armed are shown in plate 5; of these figure B represents Cyathea 
onusta, and figure C, C. aureonitens, both species of Costa Rica and 
western Panama. The last mentioned is one of those which really 
produce spines upon the trunk also, and these, like those of the stipe, 
of needlelike sharpness. In certain species the spines are long, 
straight, columnar, and blunt; in others low and broadly conical, with 
a hooked point; in still others slender and sharp, but very short and 
closely set. The conical, more or less curved form is the commonest 
one among North American species. In Cyathea arborea (pl. 5, fig. A) 
they are evident only as low tubercles, and in not a few others they 
are altogether lacking. They are usually produced only upon the un- 
derside of the stipe, in some species extending in lessened size and 
number along the rachis well toward the apex of the blade, as may be 
seen in Alsophila aspera (pl. 7). In color spines range from yellow 
to brown, purple and black, usually taking the color of the stipe or 
presenting a darker and highly polished surface. They have been 
said to be poisonous, though the truth of this is certainly open to doubt. 
The stipe is otherwise furnished with large protective scales which, 
however varied in character, are as distinctive for each species as are 
the spines of each. These scales closely invest the apex of the crown 
in a thick, upright, brushlike mass. The young fronds, like those of 
all ferns, as they unroll from the bud carry with them their scaly 
covering. (Plate 6 represents at natural size a young expanding 
frond of Cyathea arborea.) The great majority of the large scales 
which develop upon the frond as it increases in size are, however, 
readily deciduous; and as arule only those of the lower stipe, and more 
especially those which are seated in the deep axils of the stipe bases, 
persist until the frond attains maturity. The latter are precisely 
like those of the crown, of which, in fact, they are really an integral 
part. Thus constituted, the cap or head of the crown consists ordi- 
narily of scales so closely packed together that they serve as a very 
effective, impervious, protective covering, not only against excessive 
moisture and consequent infection from without, but also as a safe- 
guard, enabling the plant to maintain without interruption its vital 
activities at the one essential point, the apex, despite unusual ex- 
tremes of dryness, heat, and cold. The utility of the chaffy cap is 
