1052 
de Frame . — On the Struchire and 
occur in the midst of dead suberized tissue. If this be the case, then, 
the cork, and in some cases deeper seated tissues also, must have suffered 
destruction. 
In any one section the zone of secondary cortex never extends in 
a continuous band round the vascular structures, but is found in arcs 
of greater or less extent. The fact that, in the upper region of the series, 
cork-cambium formation can be traced in what is obviously an old stem 
suggests that the phellogen may have had only a comparatively short 
period of activity before it was replaced by a new, more deeply placed arc 
Text-fig. 18. a. Beginning of phellogen formation, x 70. b. Later stage of cork cam- 
bium development, x 55. c. — cambium; s.c. = secretory element; f.s. = fibrous strand; o.s. — 
direction of cortex ; i.s. = direction of stele. 
of meristem ; so that by successively formed layers of cork, each more 
deeply placed than the last, the stem would in time be composed only of the 
vascular cylinder and the last formed cork formations, a condition arrived 
at in the new stem of Sutcliffia , where practically all the cortex and the 
leaf-bases have been sloughed off as bark. 
It is of great interest to record in this connexion, that Dr. Scott , 1 who 
very kindly examined two or three of my sections, remarked, ‘ I sometimes 
find very distinct bands of meristem in the cortex of my Sutcliffia , but they 
look more like the beginning of periderm than of vascular tissue. The 
inner cortex generally is very delicate and fit to originate meristems.’ 
1 In a letter to Professor F. W. Oliver on June 22, 1912. 
