Dimorphic Anthers of Lager stroemia indie a. 503 
weighings were made every few minutes, in Fig. 1. The rate of loss for 
the red anthers is represented by the upper curve, while the rate for the 
yellow anthers is shown by the lower one. The difference in the total 
relative water loss of the two types of anthers is clearly shown by the 
(shaded) difference between the two curves . 1 In each case the red anthers 
lose far more rapidly than the yellow. 
Such loss cannot of course continue indefinitely. After the red anthers 
have lost a considerable part of their water, the rate of loss from the other 
type must become higher, until finally both types are air dry. This is 
clearly shown in a second set of diagrams, Fig. 2. In these the abscissae 
represent hours, while the heights of the ordinates erected at various intervals 
show the percentage loss of water by the red anthers minus the percentage loss 
by the yellow anthers. After a few hours the loss by the red anthers is far 
in excess of that by the yellow. Finally, the difference becomes practically 
zero. 
IV. Nature of the Physiological Differentiation 
of Anthers. 
The immediately underlying cause of the physiological, peculiarities 
which have been demonstrated to characterize the morphologically differ- 
entiated anthers must be either physical or chemical. 
Possible physical factors are dissimilarities in form, resulting in the 
exposure of widely different surfaces to evaporation, or differences in 
the histology of the superficial layers, which are capable of modifying the 
amount of water lost by evaporation. Both types of anthers are of roughly 
the same form. I have not made critical histological comparisons, but the 
sections I have seen indicate that there are at least no conspicuous differences 
between the two types. 
Thus, comparatively considered, the evidence for a physical basis 
of the observed differences is quite negative. Quantitatively examined, 
the data are strongly opposed to such an assumption. The large anthers 
are of about the same form as the small ones. The ratio of the surfaces of 
the two types of anthers will be closely enough 
Sr\Sy\:{^Vif:\^Tyf, 
where Fr, Vy are the volumes of the red and yellow anthers respectively. 
Volume may for all practical purposes be taken as the equivalent of 
weight, provided the two types of anthers have the same percentage water 
content. 
In the experiments entered in Tables A-C the anthers were not 
allowed to dry completely ; hence the total water lost by the red is far in 
1 These are merely draughtsman’s curves, secured by fitting a spline as closely as possible to the 
data given in the tables. 
