Anatomy of the Cone and Fertile Stem of Equisetum. 245 
about twice as great as at the level of Series A (cf. p. 248) of the same cone, 
so that the distance at which the pull originates may well have weakened 
its effect a good deal. Further, the degree of reflection of the sporangio- 
phores is itself less in Series B than in Series A. The probability that the 
pull of a reflexed sporangiophore is an important factor in bringing about 
the downward divergence of the traces is supported by the fact that in most 
c. 
k 
_c 
'e. 
c. 
... 
. 
C. 
avb. 
-v! 
c. 
xsp. avb. 
N 
avb. 
c. 
•sp. axk 
c X 
1 . z. 3 4. 
19. £Q. 2.1. 21a. 
Text-fig. 2. Divergence of traces of Series A of Cone A. x 13^. Lettering as in Text-fig. 1. 
Note that traces 5 a, 5 b, and 21 a die out in the cortex. 
cases, though there are numerous exceptions, the downward slope of the 
outgoing trace is much steeper towards the periphery of the cortex, 
i. e. nearer to the object exerting the pull. This is especially true of 
Series A of Cone B, where, if there is any difference in the steepness of the 
course of the trace, the outer part is always the steeper (cf. Text-Figure 1). 
But I do not think that the reflection of the sporangiophores is the 
only cause leading to the downward divergence of the traces. In the 
