SYMMETRY OF THE CENTROSPERM X. 287 
Both internode-curves show an initial ascent, succeeded in order by a descent, an 
ascent, and a final descent. "These general features are more or less disturbed by minor 
sudden rises and falls. To what extent the irregularities are due to external circum- 
stances it is impossible to say. Itis worthy of note that the first maximum and the 
first two minima occur in the subterranean part, so that etiolation does not overpower 
other influences that aid in determining the internode-lengths. The ascents and 
descents in the curves are not of the sudden and repeated kind characteristic of leaf- 
displacements (all the leaves were in opposite pairs), but are generally of a more gradual 
type, suggesting partly innate characters and partly characters induced by temporary 
change in environment. 
AIZOACEJE. 
The genus Mesembryanthemum includes opposite- and alternate-leaved types. The 
two species that I examined belonged to the opposite-leaved type. The curves, if not 
quite regular, showed irregularities of only minor extent and gradual form, such as 
might easily be due to slight variations in the surroundings or to the different ages of 
the internodes. 
MESEMBRYANTHEMUM ECHINATUM. (Curves 14 1-11.) 
Two branches inserted at neighbouring nodes of the same relatively main axis 
were measured from the base up to the terminal active bud. The following are the 
measurements obtained :—- 
Branch I :—8, 4:25, 10, 14, 11:5, 95, 11, 14°5, 12, 10:5, 8:5, 9, 9, 7:25, bud. 
Branch IT :—8, 2:5, 7, 13, 12, 12, 10, 12:5, 14, 9:5, 6:5, 8, 8, shorter internode and bud. 
141. 14 n. 
Both the internode-curves show an initial rise, followed by a fall, a rise, fall, rise, fall. 
The final descent, in any case, is due to the immaturity of the internodes. 
MESEMBRYANTHEMUM FILAMENTOSUM. (Curve 15.) 
A seedling of this species was uprooted, and the measurements, commencing at the 
cotyledonary node, were as follow :—2°5, 10:5, 16, 14, 12°5, 11, 10°5, 12, 10°5. 
