300 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Carmaceae: Canna x William Stone. 
Marantaceae: Maranta Leitzii (pi. 19, fig. 92). 
Gynandrae. 
Among the few terrestrial orchids the roots of which were 
examined, the following have specialized hair cells : Arethusa bul- 
bosa (pi. 19, fig. 96), Calopogon pulchellus , Pogonia ophioglossoides 
(pi. 19, fig. 93-95). 
Nymph ae ace ae. 
A large number of Dicotyledons were studied, including many 
aquatic species. The Nymphaeaceae alone have trichomes prede¬ 
termined in the formative region of the root tip. In species of 
Brasenia, Cabomba, Nuphar, and Nymphaea, the history of the 
root-hairs is like that of the same organs in the Monocotyledons 
which have been described above. 
Nymphaea dentata (pi. 19, figs. 97-101). —The trichoblasts 
arise as narrow proximal segments in the transverse division of 
epidermal cells under the root-cap. These short cells have a high 
staining capacity, and are brought out strongly by the application of 
iodine. At the edge of the root-cap they are seen in longisection 
as granular cells with straight transverse walls, between the con¬ 
siderably elongated prismatic non-piliferous cells (pi. 19, fig. 97). 
The whole exterior wall is concerned in the outgrowth of the hair 
(pi. 19, fig. 100). The foot of the latter therefore covers the whole 
cell (pi. 19, fig. 101). The hairless cell becomes very long. The 
two kinds of cells alternate regularly. 
The short cell may remain non-piliferous. In this event it may 
elongate somewhat and form a constituent of the epidermis differing 
from other cells only in length. Or it may become wedge-shaped, 
the edge outward, and by the pressing together of the adjacent 
cells in the row be pushed inward until the ends of the elongated 
cells meet above it and it no longer appears as a superficial element 
(pi. 19, fig. 97-99). This submergence of the trichoblasts was seen 
in Nymphaea odorata and N zanzibarensis as well as in N. dentata. 
In addition to the species already named, the following were seen 
