518 Shove.—On the S'truehire of the 
are crushed together to form a protective tissue. Among 
these crushed elements occur at intervals short lignified cells ; 
these are thick-walled, with pointed ends, and probably 
function as idioblasts for mechanical support. 
In two cases, probably anomalous but certainly of interest, 
the roots of Angiopteris showed dichotomous branching. The 
first case was that of a large air-root obtained from the 
Cambridge Botanic Garden ; the two branch-roots produced 
by the dichotomy of this measured only about i cm. in 
length, hence their vascular elements had not been differen¬ 
tiated, and in fact the branches could be hardly said to con¬ 
stitute more than root-tips. The mother root was i cm. in 
diameter, and possessed twenty protoxylem-groups, the outer 
elements only of the xylem-rays being lignified. In this case 
the connexion between the protoxylem-groups of the mother- 
root, and of its branches, could not be determined, owing to 
the non-lignification of the protoxylem in the secondary roots, 
but in the second case of dichotomy observed the relation 
was satisfactorily worked out. 
The dichotomous root in question was a side-branch of an 
earth-root, also from the Cambridge Botanic Garden. The 
main root was *65 cm. in diameter, possessed thirteen groups 
of protoxylem, and had lignified tracheides half-way to the 
centre. This produced a side-root, -25 cm. in diameter, pos¬ 
sessing seven protoxylem groups, which shortly after its exit 
from the cortex of the mother-root underwent dichotomy. 
The products of the division were roots, -2 cm. in diameter; 
each possessed five groups of protoxylem, and its xylem- 
elements were lignified half-way to the centre. Fig. 30 shows 
a transverse section of the side-branch just after its exit from 
the main root; the xylem groups A, B, C are larger than the 
others. Fig. 29 shows the stele of the side-root undergoing 
dichotomy; the xylem groups A, B, C have each divided 
into two ; A has given rise to 1 and 2, B to 3 and 4, and 
C to 5 and 6 . Two new steles have been formed, each con¬ 
taining five groups of protoxylem. 
This method of branching is certainly not general in the 
