Oliver . — On Sar codes sangitineci , Torr . 309 
in the hyphal zone. Proceeding outwards, the texture of the 
mycelium becomes looser, and it no longer forms such a dense 
pseudo-parenchyma. The individual, septate, tubules (hyphae) 
are distinguishable, and at the periphery their ends turn 
radially outwards, terminating blindly in a manner resembling 
root-hairs. 
It will be well now to describe the relation of the parts at 
the root-apex before treating of the phenomenon of myco- 
rhiza in greater detail. Fig. 43 represents a longitudinal 
median section of a root-apex of Sarcodes. Right and left, 
low down, the columnar epidermal layer is seen ( ep ). It may 
be easily followed right up to the apex, where it is covered in 
by the several layers of the root-cap. Indeed the root-cap 
arises in common with the epidermis, being formed from it 
by repeated tangential divisions. The inmost, and youngest, 
layer of the cap ( rc ) is shown as having arisen quite recently 
in this way. Each layer of the root-cap in turn has originated 
in this manner, as an examination of Fig. 43 will show. Each 
extends a little further down the root than the one inside it, 
the fifth or sixth layer forming the outermost functional layer 
of the root-cap. The older layers have separated some little 
way from these by the ingrowth of the mycelium, and are still 
held there as described. In Fig. 43 they are not represented. 
The dermato-calyptrogenic layer is quite distinct from the 
initial group of periblem and plerome cells. These latter 
arise in common, and it is only a little way backwards that 
the distinction between them becomes manifest — the cells of 
the plerome undergoing longitudinal division more frequently 
than those of the periblem. Such a grouping of the cells at 
the root-apex is likewise found in Monotropa. The cap, 
however, in this latter genus is exceedingly thin, being only 
one or two cell-layers thick h 
The apex of the root is everywhere enveloped in the 
mycelium. In this point Sarcodes differs from Monotropa. In 
Monotropa the extreme tip is quite bare, and the fungus is 
1 Cf. Kamienski, 1 . c., PI. I. Fig. 5 : also p. 11. 
