464 Agnes Arber. — Studies on Intrafascicular Cambium 
Methods.* 
In cases where it has been necessary to use dried herbarium material 
for sectioning, I have employed the method of preparation devised by 
Dr. R. C. McLean. 1 The basis of this method is prolonged treatment with 
dilute solutions of caustic potash. For purposes of economy I substituted 
impure waste spirit (less than 90 per cent.) for the absolute alcohol recom- 
mended by McLean for the first stages of his process, and I also dispensed 
with an air-pump, but in spite of these modifications the method gave most 
successful results, even with such delicate structures as the inflorescence 
axes of the Triuridaceae. The treatment of the material took place in 
a room which was kept at such high temperatures that the fluids nearly 
always felt tepid to the touch, and I think that this continuous warmth 
probably assisted the recovery of the tissues considerably. 
Summary. 
III. 
Attention is drawn to the development of the leaf-bundles in Veratrum 
album L., because this is the only case among Monocotyledons (except that 
of the tubers of Gloriosa superba described by Queva) in which an intrafas- 
cicular cambium formed in one year has been observed to persist through 
the winter and to function in the succeeding year. These bundles also show 
a clear differentiation between primary metaxylem and secondary xylem 
consisting of a group of elements of smaller calibre. The same differentia- 
tion has been observed in varying degrees in a number of other Mono- 
cotyledons. There is some evidence that it is usual for the xylem of the 
lateral veins to be attached exclusively to the secondary xylem of the 
bundles from which they arise. 
IV. 
The existence of intrafascicular cambium is recorded for the first time 
in the Juncaceae, Haemodoraceae/ Amaryllidaceae, and Cyclanthaceae. 
The Monocotyledonous families in which it is known now number nineteen. 
I pointed out in 1918 that cambium had then been recorded in nine out of 
the eleven Cohorts of Monocotyledons. In the present paper I have been 
able to establish its existence in a tenth Cohort, the Synanthae. In the 
case of the extremely reduced bundles of the eleventh Cohort — the Triuri- 
dales — the arrangement of the elements suggests a vestigial trace of cambial 
activity. This group can therefore scarcely be regarded as forming an 
exception to the general rule that intrafascicular cambium occurs in all the 
Cohorts of the Monocotyledons. 
1 McLean, R. C. : The Utilization of Herbarium Material. New Phyt., xv, 1916, pp. 103-7. 
