630 
XYLOPHYLLA 
Xylophylla Linn. = Phyllanthus Linn, (the sp. with phylloclades). 
Xylopia Linn. Anonaceae (6). 60 sp. trop. 
Xylopleurum Spach = Oenothera Linn. 
Xylosma Forst. f. = Myroxylon Foist. 
Xyridaceae. Monocotyledons (Farinosae). 2 gen. (Xyris, Abolboda) 
with 50 sp. trop. and subtrop., mostly Am. Mostly marsh plants, 
herbaceous, tufted, with radical sheathing leaves and spikes or heads 
of 5 firs. Perianth heterochlamydeous. K 3, the lateral sepals small, 
the anterior large, enclosing the cprolla; C (3). Sta. 3, epipetalous, 
the outer whorl absent or represented by staminodes. Ovary i-loc. 
or imperfectly 3-loc., with parietal or free basal placentation and 00 
orthotropous ovules. Embryo small, in mealy endosperm. Placed in 
Coronarieae by Benth. -Hooker, in Enantioblastae by Warming. [See 
review in Bot. Gaz. 1893, p. 313-] 
Xyrideae (Benth. - Hooker) = Xyridaceae. 
Xyris Gronov. ex Linn. Xyridaceae. roo sp. trop. and subtrop. 
Yucca Dill, ex Linn. Liliaceae (vi). 20 sp. Southern U.S., Mexico, 
&c. Many are hardy in this country (Adam’s needle). The stem is 
short, growing in thickness, and branching occasionally (cf. Dra- 
caena) ; at the end is a rosette of leaves, the old ones dying off below. 
The leaves are fleshy and pointed. The firs, are large and white and 
form a big panicle. Their chief interest is the very remarkable mode 
of pollination (for details and figures see Riley in 3 rd Ann. Rep. 
Missouri Bot. Gdn. 1892). This is one of the few cases of mutual 
dependence and adaptation of a single flr. and a single insect — Pro- 
nuba, a moth. The white flr. emits its perfume especially at night, 
and is then visited by the moths. The female has a long ovipositor 
with which she can penetrate the tissue of the ovary of the flr., and 
possesses peculiar maxillary tentacles confined to the genus, which are 
prehensile and spinous. “ Her activity begins soon after dark, but 
consists, at first, in assiduously collecting a load of pollen. She may 
be seen running up to the top of one of the stamens.... The maxillary 
palpi are used in this act very much as the ordinary mandibles are 
used in other insects, removing or scraping the pollen from the 
anthers towards the tentacles. After thus gathering the pollen she 
raises her head and commences to shape it into a little mass or 
pellet....” She repeats the operation on several firs., until she has a 
pellet about thrice as large as her head. The moth then flies to 
another flr. and proceeds to deposit a few eggs in the ovary, piercing 
its wall with her ovipositor. Having done this she climbs to the top 
and presses the ball of pollen that she has gathered into the stigma. 
The result is that the ovules are fertilised, but they are so numerous 
that there are plenty for the larvae to feed upon and also to reproduce 
the plant. 
The leaves of Y. filamentosa L. and other sp. furnish an excellent 
fibre (cf. Agave). 
