460 Agnes Arber. — Studies on Intrafascicular Cambium 
a fibrous sheath (Fig. 3, f), interrupted in the region between the xylem 
and phloem. The phloem is remarkable for the arrangement of its elements 
in extremely long radial files — an evidence of an unusual degree of cambial 
activity. The xylem consists of three highly distinct types of element — 
protoxylem (px.), large lumened metaxylem (mx.) and, on the side 
towards the phloem, a zone of elements of much smaller calibre with 
scalariform sculpturing (xy 2 .). This occurrence of relatively narrow, ligni- 
fied elements, adjacent to the larger metaxylem vessels on the phloem side, 
is not infrequently seen in transverse sections of the leaves of Mono- 
cotyledons, though it is seldom so strikingly displayed as in Veratrum 
album. I have observed it, for instance, in varying degrees, in examining 
sections of the following species : 
Liliaceae. 
Albuca nelsoni N. E. Br. 
Allium fistidostim L. (Fig. 4). 
A. p or rum L. 
A. ursinum L. 
Anthericum sp. 
Arthropodium panicidatum R. Br. 
Colchicum byzantinum Ker-Gawl. 
Hemerocallis fidva L. 
Hyacinthus (garden var.). 
Kniphofia caidescens Baker. 
P hormium tenax Forst. 
S cilia hispanica Mill. 
Smilax laurifolia L. 
Veratrum album L. (Fig. 3). 
Haemodoraceae. 
Anigozanthos sp. (Fig. 5). 
Amaryllidaceae. 
Crinum sp. 
Cyrtanthus sanguinea Walp. 
Narcissus pseudo-narcissus L. (garden var.). 
Iridaceae. 
Crocus (garden var.). 
Iris orckioides Carr. 
I. sisyrincliium L. 
/. sp. 
Moraea polystachya Ker-Gawl. 
ZlNGIBERACEAE. 
Hedychium sp. 
In most of the cases enumerated in the above list it is difficult, owing to 
