328 Dr. G. Ogilvie on the Vascular 
ciculus with a double origin from the netted cylinder, but with- 
out any dark sheath. 
The rhizome is of pale tissue, except the cuticular layer, and 
one of brownish cells round the fasciculi of the netted cylinder. 
Scolopendrium vulgare. 
The petiole has two fasciculi uniting above in the midrib of 
the frond, and separated below by two half-sheaths of dark 
tissue, united by their convexities. Externally also the fasci- 
euli are bordered by dark lines, which run down into the 
rhizome. 
The rhizome is of pale tissue, except the cuticular layer and the 
lower ends of the outer dark lines of the petioles just mentioned. 
Ceterach officinarum. 
The petiole has two fasciculi, which unite above in the midrib 
of the frond, and three lines of dark tissue, which run down 
into the rhizome—two laterai, on the outer margins of the fas- 
ciculi, the other median, forming two half-sheaths, united by 
their convexities. 
The rhizome is of pale tissue, except the cuticular layer and 
the inferior extremities of the petiolar lines just noticed. 
Pteris aquilina. 
The petiole has numerous anastomosing fasciculi derived from 
the outer and inner systems of the rhizome, also a main central 
plaited band of dark fibrous tissue (connected with those of 
the rhizome), and some subsidiary tracts arising within the 
petiole. 
The rhizome has a white pulpy parenchyma, with a hard 
cortical shell of dark tissue, and two longitudinal dark bands 
within, separating an inner vascular system of two flat bundles 
from a more external, which consists of numerous small fasci- 
culi anastomosing sparingly to form an irregular wide-meshed 
cylinder. 
Allosorus crispus. 
The petiole has a single fasciculus without a dark sheath, and 
a double vascular cord. 
The rhizome consists in part of pale tissue, with a brown 
cuticular layer, but it contains also dark tissue internally—as a 
central cord along the axis, and as faintly-marked sheaths 
round the fasciculi of the netted cylinder. 
Blechnum boreale. 
The petiole has two fasciculi, imbedded in the pale tissue of 
the interior, which towards the base is reduced to a mere sheath 
