194 
WILLIS : PODOSTEMACBÆ 
number of specimens usually discloses the fact that hardly 
any two are alike in this respect. In Lawia the spathe is 
physiologically represented by the cupule, an organ of 
apparently axial nature bearing leaves, and often closed 
until exposed by the fall of the water. In Tristicha 
ramosissima the construction is still more primitive and 
the flowers emerge through the water like those of the 
water Ranunculi. 
llie Pedicel . — The young flower is enclosed within the 
spathe or cupule, and has practically no pedicel. When the 
spathe splits the pedicel elongates more or less, sometimes to 
as much as 5-6 mm., before the flower opens, but often only 
just enough to let the flower stand nearly erect in the spathe. 
After anthesis the pedicel usually lengthens while the fruit 
is ripening, and at the same time the outer pellucid cortical 
tissue falls away or shrivels, while the central tissue 
becomes woody, leaving the fruiting pedicel much thinner 
than the flowering one, only the central lignifled tissue — the 
vascular tissue and the inner cortex — persisting. Sometimes 
part of the outer cortex remains on the lower part of the 
pedicel and has been mistaken for a spathe. The length of 
the ripe pedicel is variable, and the average of a large number 
of specimens should always be taken ; it seems to be affected 
by the rate of fall of the water, the steepness of the rock, 
and other factors, and requires further investigation. The 
fruits ripen very rapidly, and even after gathering may 
ripen in pressing, so that the condition of the flower and 
length of pedicel in herbarium material is singularly 
untrustworthy. The leaves or bracts below the flower fall 
away with the cortex of the stalk in many species ; this is 
especially well marked in Willisia selaginoides, whose 
fruits, really sessile, often appear to be provided with long* 
pedicels. 
The Flower . — The parts of the flower are, as a rule, very 
constant in number and arrangement, but some features vary 
greatly, and it so happens that considerable taxonomic stress 
