284 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Filices. 
In most of the true ferns, the roots of which were studied, the 
hair-cells are ordinary epidermal cells. A list of the species is given 
above. The following proved exceptional : 
Schizaeaceae: Aneimia adianti folia, A. fraxinifolia, Lygodium 
dichotomum. 
Aneimia adianti folia (pi. 16, fig. 1—3). — In sections of a cer¬ 
tain actively growing root, the cap extends over about 40 cells of the 
epidermis, counting in a single longitudinal cell series. At its edge 
the hair-cells appear in longisection as short, somewhat wedge-shaped, 
dark cells, whose outer walls project somewhat from the general sur¬ 
face of the epidermis. Following the layer toward the apex, a series 
of cell-pairs can be seen, ending with the 22d cell from the growing 
point. Here by a recent transverse division the first of the cell-pairs 
has been formed from a mother cell, the distal member being the 
longer in the ratio of 2: 1. The proximal, shorter, and very slightly 
wedge-shaped cell is the trichoblast. 
A few cells back of the root-cap, the atrichomic cells are seen in a 
much elongated condition (pi. 16, fig. 2). The trichoblasts have 
become elongated to a less degree, and are broadly triangular in out¬ 
line. As they develop, the hairs are directed obliquely toward the 
root tip. The base of the trichome is wedge-shaped. 
Only the three species of the Schizaeaceae named above were 
available for examination. They agree very closely in the appear¬ 
ance of their trichomes. 
Hydropterideae. 
Azolla caroliniana and A. filiculoides agree in the origin and 
character of their root-hairs. 
The root is provided with a root-cap of two cell layers. The outer 
is much the shorter and except at the apex is separate from the inner. 
The latter forms at first a close covering for the trunk. The initials 
of the trichomes arise within a belt of actively dividing cells, lying 
immediately under thQ inner root-cap, not far from the apex, at an 
actual distance varying with the rate of growth of the terminal region 
(pi. 16, fig. 4, T). The division is oblique. Only the final stage 
