252 de Fraine . — The Morphology and Anatomy of the 
Some idea of the abundance of these mucilage glands can be gained 
from Text-fig. 5, which is taken from the apex of a Main bank plant. 
The effect of this abundantly secreting surface in keeping the apex and 
buds bathed in mucilage must be of enormous value in preventing desiccation 
by checking too rapid transpiration. 
In S’, be lli difolia the mucilage glands are few in number as compared 
with S. binervosa. 
While in full agreement with the general observations of Wilson as 
Text-FIG. 5. Transverse section of part of the apex of a main bank plant of S. binervosa. x 36. 
Mucilage glands black ; vascular bundles dotted ; B = bud ; M = Mettenius gland. 
to the structure of the mucilage glands, certain details may be added to his 
description. 
Concentrated sulphuric acid has no action on the gland cells, while 
chi or. zinc, iodide produces a deep brownish-yellow coloration, so that the 
cells appear to be cuticularized (Text-fig. 6, c). This cuticularization of 
glandular tissue recalls the similar phenomenon described by Salisbury 1 in 
the extra-floral nectaries of the genus Polygonum, and further the glands 
figured by him show a close resemblance to the mucilage glands of the 
Plumbaginaceae. (Compare Figs. 2 and 4 of Salisbury’s paper with our 
Text-figs. 6 B and 6 A.) 
1 Salisbury, E. J. : The Extra- Floral Nectaries of the Genus Polygonum. Ann. Bot., vol. xxiii, 
I 9°9> P- 2 37« 
