and Woody Tissues of Ferns. 321 
terposed between them and the dark cortical portion of the stem, 
it is hardly possible to separate the vascular coat in the same 
way from the delicate cellular tissue of the medulla which it in- 
vests. (Pl. V. fig.3; compare with fig. 4.) 
The rhizomes of Hymenophyllum Tunbridgense and H. Wil- 
soni are of interest from presenting a transition to the type of 
stem characteristic of the Lycopodiacez, as there is but a single 
vascular bundle, lying in the axis of the bristle-like rhizome 
(PL VI. fig.5). This central fasciculus contains four or five 
scalariform vessels, surrounded by a cambium-layer. Round 
this, again, there is a thin stratum of pale parenchyma, and a 
cortical layer of brown tissue, fibrous and much indurated inter- 
nally, but loose and chaffy on the exterior. The transition-cha- 
racter of the stem is of the more interest that we have in it 
all the essentials of the rhizome of Osmunda. We have only to 
conceive the stout caudex of the latter drawn out till it is reduced 
to the thread-like dimensions of the rhizome of Hymenophyllum, 
to have a complete transformation of the one into the other; 
for when the vascular cord of Osmunda is reduced to the dimen- 
sions of that of Hymenophyllum, its cellular pith necessarily 
disappears, as a single series of vessels of the ordinary thickness 
must come to occupy its whole diameter. 
In all the stems noticed above, with the dark tissue much 
developed, and particularly in Osmunda regalis, Blechnum boreale, 
Pieris aquilina, and Allosorus crispus, there is a very remarkable 
contrast between the hardness of the coloured tracts and the 
great softness and delicacy of the pale parenchyma and of the 
vascular bundles (especially in their cambium-layer). The close 
juxtaposition of tissues of such different powers of resistance 
adds much to the difficulty of obtaining thin sections for inicro- 
scopical purposes. The permanency of these tissues is in pro- 
portion to their hardness. Thus in the rhizomes of the com- 
mon Braken, after long exposure the cortical layer and the two 
internal bands of dark substance are sometimes the only parts 
left, the pale parenchyma and the vascular bundles having all 
disappeared by the process of natural decay. And when this 
dark substance forms the main element, as in Osmunda and 
Blechnum, the whole rootstock has a like protracted duration, as 
has been already observed of the former species. 
In connexion with this subject, the question suggests itself, 
whether the hard brown tissue now referred to (or pheenchyma, as 
it might be called) corresponds to the proper wood of the higher 
or phanerogamic plants? There is some difficulty in answering 
this question, arising principally out of the ambiguity of the 
term “woody tissue.” I do not see any reason to doubt that in 
many of the higher plants there are hard parts, commonly called 
