212 Seward . — On Rachiopteris Williamsoni sp. nov ., 
bundle is shown in Fig. 8 ; here there is an elliptical group of 
tracheids and xylem-parenchyma, with distinct protoxylem- 
elements at p ; at ^ is a small space such as frequently occurs 
in the immediate neighbourhood of protoxylems, and which 
doubtless owes its origin to tearing. The surrounding phloem- 
tissue is exceptionally well preserved, and the regularly 
arranged canals are very distinct. In the fundamental tissue 
four larger canals are shown in the figure, and on the bundle- 
side of each is a larger or smaller stereome-strand. 
Fig. 9 affords a good illustration of the structure of a vas- 
cular bundle as seen in longitudinal section. In the centre are 
wide scalariform and reticulate tracheids, with rows of long 
and narrow xylem-parenchyma (‘ amylom ’) cells at a. At 
ph are the narrow cambiform elements of the phloem, with 
one of the small canals at c. None of the longitudinal 
sections of these phloem-canals reveal the existence of trans- 
verse or oblique walls ; in some places, as at b , there are 
obliquely-running lines in the canal-cavity, but on closer 
examination these resolve themselves into cracks in the crys- 
talline material filling up the canals. The walls of the phloem- 
elements are usually somewhat crushed, but the preservation 
is, on the whole, remarkably good ; most of the phloem- 
elements are of the cambiform type, and there are no indica- 
tions of sieve-tubes. The canals appear to belong to the 
peripheral part of the phloem rather than to the fundamental 
tissue. At f are the cells of the latter tissue arranged in 
vertical rows, at g one large canal with the usual black 
contents, and at m the elongated elements of the stereome- 
strand. On the opposite side of the bundle at n there is 
a longitudinal section of what may probably be considered 
a sac-like receptacle, comparable to the mucilage-sacs of 
Angiopteris and other Ferns. 
The section in Fig. io shows spiral protoxylem-elements at 
p, and at t a larger scalariform tracheid, with rows of xylem- 
parenchyma at a ; the wall w does not belong to the underlying 
spiral element, but to some of the parenchymatous cells 
resting on its surface. 
