586 Tkoday. — Behaviour during Drought of the Leaves of two 
Observations in the field, made subsequently to much of the experi- 
mental work described in this paper, make it clear that two forms are to 
be distinguished among the plants that had been used, one of which is 
almost certainly Passerma filiformis , Linn. ; the other resembles P. falcifolia , 
C. H. Wright, though it does not agree in all respects with Wright’s 
description in the ‘ Flora Capensis \ 1 
The former commonly reaches a height of four or five feet. It has 
numerous erect branches and more or less adpressed leaves, decussately 
arranged and, when young, closely adpressed to one another in four 
conspicuous ranks. 
The other form has a more spreading, bushy habit ; the leaves are 
longer, and are not adpressed except when young, but spread at an angle of 
45 0 or more from the stem. 
In much-shaded ’ situations, plants belonging to the latter form are 
found with a very lax habit, with leaves spreading still more widely and 
branches slender and straggling. 
In both forms the leaf is grooved on the upper side, the groove being 
thickly lined with close, woolly hairs. When the leaves are adpressed 
the groove is brought near to the surface of the stem, which is pubescent 
when young. 
In herbarium material the leaf-grooves are tightly closed so that the 
leaves appear acicular. 
Closure of the Groove and Water Content . 
In the dry season (from January to March) the grooves are narrowed 
by the approximation of the two sides of the leaves, until the edges may 
meet over the groove and completely enclose it. Closure proceeds from 
the tip towards the base, where communication with the outer air is 
maintained except in extreme drought. 
The following experiment shows how closure is correlated with 
diminishing water content : 
A shoot was brought to the laboratory in the latter part of February, 
1920, and kept in a full vasculum, weighed the following day, and then put 
with the cut end of the stem in water under a bell-jar. Most of the leaves 
had their grooves tightly closed. By the next day they had opened well. 
After another day the shoot was finally weighed and its dry weight 
determined. The results are given in Table I. 
1 P. falcifolia is described as having t-he bracts densely woolly within. In my specimens there is 
only a narrow band of woolly hairs, continuous with the groove of the narrow leaf-like apex, while 
the wings are glabrous. No record of P. falcifolia from the Cape Peninsula is mentioned in Flora 
Capensis, and Bolus and Wolley-Dod (loc. cit.) did not separate the form in question from 
P.filifor?nis . The leaf characters, however, are more like those of P. falcifolia and distinguish it 
from all the other species described. 
