ee 
Gt 
See. 
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DISSEMINATION AND LEAF REFLEXION OF yucca. 109 
is common in cultivation it very seldom fruits and has not 
been much studied. 
Brevifolia differs from other known species in having a 
very thick exocarp similar to that of alotfolia but which on 
maturing becomes dry and spongy instead of pulpy. What 
is known of the dissemination of this species is from the 
observations of Dr. Trelease:* ‘‘ The fruits of this species 
fall quickly after ripening either by a distinct disarticulation 
or because of the brittleness of the pericarp at the base, 
and their rounded form and very light specific gravity 
render them well-developed ‘tumble fruits’ and point to 
their dissemination over the dry sands of the desert by aid 
of the strong winds which prevail there, the seeds being 
liberated ultimately by the breaking of the fragile pericarp.”’ 
The Chaenoyuccas or capsular species, which have dry 
erect capsules and light, strongly compressed seeds, are 
typical wind-disseminated plants. The capsules open by a 
gradual septicidal dehiscence from above downward and by 
a dehiscence for acertain distance from the top through the 
backs of the carpels ( Plate 47, fig. 5). 
The seeds are very thin and flat, ranging in thickness 
from .5 to 1.5 millimeters, and have a very slight wing (Plate 
47, fig. 6), a flying apparatus of the simplest kind similar 
to that in Iris, Tulipa and Agave.f They are arranged in 
six rows and are gradually sifted out of the erect capsules 
by the shaking of the fruit cluster by the wind or animals 
and by the wind dipping into the open top of the cells. 
The device is thus to secure the gradual scattering of the 
seeds, a few at a time by gusts of wind, the wind serving 
to carry the seeds for some distance. 
The peduncle of the capsular species is usually quite 
long, serving to raise the fruit cluster free of obstruction 
to some height above the surrounding vegetation. /ilamen- 
tosa and glauca, the most widely known capsular Yuccas, 
* + Trelease, Wm., ‘‘ Further Studies of Yuccas and their Pollina - 
tion,’’ 1. c., p. 224. 
+ Hildebrand, ‘ Verbreitungsmittel der Pflanzen,’’ p. 16. 
