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DISSEMINATION AND LEAF REFLEXION OF yucca. 101 
lateral shoots form the uppermost phytomeroid. As the 
fruits which they bear ripen and lateral buds in turn start 
at the base of their fruit stems, they cease to be the terminal — 
phytomeroids and their leaves begin to reflex. 
The leaves of the upper phytomeroid while in the 
erect stage are separated by a wide angle of divergence 
from the reflexed leaves of the preceding phytomeroid, 
the point of divergence being usually very marked (Plates 
45 and 46). 
The phytomeroids of the trunk are usually from one 
to two feet in length and easily distinguishable even in 
the old lower growths. A slight swelling in the trunk fre- 
quently marks the place where one growth ended and the 
next began. 
The reflexing of the leaves is evidently due to a strong 
epinastic growth of the tissue at the base of the leaf. 
The tissue on the under surface at this point collapses 
under the pressure exerted and becomes somewhat 
wrinkled. 
The time occupied in the reflexing of the leaves of a 
phytomeroid varies considerably. The first marked reflex- 
ing takes place quite rapidly, but the gradual drying 
and compressing against the stem is a slow action, running 
through several years. On starting to reflex, the leaves 
pass below the horizontal and come to point downward in 
from one to three months. After becoming reflexed, the 
leaves remain fresh and apparently active through the 
development of about two other phytomeroids, after 
which they begin to dry up and finally die. The length 
of time which they remain living apparently depends largely 
upon the conditions to which the plant is exposed. Plants 
growing on the sterile sand dunes along the coast or in old 
neglected yards usually have very short leaves, which after 
reflexing live only for a short period. Usually all leaves 
are found to be dried up in such cases except those on the 
two upper phytomeroids. Occasionally only those of the 
uppermost phytomeroid will be found perfectly fresh and 
