344 MISS M. G. SYKES ON THE SEEDLING AND 
distinguished the ridge-bundles from the later intercalated bundles of the leaf: he 
included both together in the “ peripheral series” *. 
Fig. 4. 
= 
PEEL LL 
i QO o , 
o eo 4549 
g 9 ao 
[v] 
(m) 
iV 
0 
0 
0 
0 
ð 
Fig. 4 represents a transverse section through the base of the leaf-groove in ‘the seedling shown in PI. 34. 
fig. 2. r,r represent the two elliptical series of bundles supplying the outer ridge; 6, 6=the row of bundles 
at the base of the cotyledonary buds; c= pair of bundles originally supplying a cotyledon. The bundles of 
each bud have a double origin from the two bundles supplying the cotyledon, in the axil of which the bud 
is borne. 
It is of some interest that the bundles supplying the ridge originate in a manner so 
similar to those supplying the leaf which the ridge subtends. Both leaf and ridge. 
receive a series of bundles which have a double attachment, being joined to one of the 
two bundles supplying each of the two cotyledons. "There thus appears to be somewhat 
the same relation between the leaf and ridge-bundles as between the cotyledon and 
bud-bundles T. 
Section VI.—CoMPARISON OF THE TRANSITION PHENOMENA IN WELWITSCHIA 
WITH THOSE IN OTHER GYMNOSPERMS. 
The peculiarities in the behaviour of the vascular system in Welwitschia depend 
largely on the extraordinary slowness of the transition from the four endarch collateral 
bundles entering the upper part of the hypocotyl to the characteristic radial structure 
of the normal diarch root, and it is probable that they are chiefly due to the unusual 
length of the swollen underground hypocotyl in this plant. 
In this connection it is interesting to refer to the seedling (Pl. 34. fig. 6) already 
described, in which the remains of the feeder were present immediately beneath the 
swollen part of the hypocotyl, and there was thus no elongated unswollen part of the 
hypocotyl developed. Here the transition was much more rapid than in the normal 
* Bower, II. pp. 581, 582. a T Ante, p. 340. 
