3io Oliver . — On Sar codes sanguined , Torr t 
entirely post-apical. This distribution, stated by various 
authors, I have been able to confirm. Embedded in the 
hyphae are found the old layers of the cap that have become 
detached (Fig. 42), and a little distance behind, where the 
epidermis is immediately presented to the mycelium (the out- 
most adherent layer of the cap ceasing here), the ingrowing 
tubules of the fungus may be seen penetrating between the 
epidermal cells in the manner shown in Fig. 44. 
These filaments never enter the epidermal cells, nor do they 
penetrate to a lower level than the base of the epidermis. 
The same arrangement is found in Monotropa . As the apex 
grows forward the outer layers of the cap continually break 
away from the underlying ones, but the mycelial layer pre- 
vents their falling away from the organ, hence they remain 
as strata — or as a series of hollow shells — kept in place, to 
even a great distance from the apex, by the hyphal layer. 
The mycelium must also keep pace in its growth with the 
elongating tissues of the root-apex ; otherwise a rupture 
would occur. 
The mode of branching of the roots of Sarcodes is ex- 
ceptional and of considerable interest. A glance at Fig. 41 
shows lateral roots arising remarkably near the apex. When 
the matter is investigated more closely it appears that all 
lateral roots in Sarcodes have an exogenous origin. Fig. 42 
shows an early stage in the development of a lateral root, as 
seen in longitudinal section. The first indication of this event 
is a slight bulging of the periblem, accompanied by a radial 
division of the overlying dermatogen. Tangential divisions 
then arise in the dermatogen and the first layer of the root- 
cap of a new lateral root is formed ( rc\ Fig. 42). The lateral 
root arises so near the apex that it is enveloped in the root- 
cap of the mother-root. In the undifferentiated tissue a 
plerome is differentiated, becoming continuous with that of 
the primary root. This takes place before the young rootlet 
commences to grow, appreciably, in length (Fig. 42). I have 
examined the insertion of a great number of lateral roots of 
all ages, but in no case does any exception occur to the rule 
