42 
PLANTS OF YELLOWSTONE NATIONAL PARK 
blue flowers. The leaves are mostly basal and shorter than the 
stem. The 6 divisions of the perianth are 2 or 3 inches long and 
petallike, as are the three branches of the style. The fruit is a 
three-angled capsule about an inch long. Found on wet lands or 
sometimes on sandy hillsides. 
SisyrincMwn angustifolium produces a cluster of very narrow, 
basal, grasslike leaves and two- 
edged stem that grows from 5 to 
15 inches high. The small, purple 
flowers are produced in a cluster 
with two sheathing, leaflike bracts, 
the outer of which is about twice 
as long as the inner and much 
longer than the flower cluster. 
The structure of the flower is 
much like that of the iris, except 
that the style branches are not 
petallike. The fruit is a nearly 
spherical capsule. 
Sisyrinchivmi ocddentale differs 
primarily in that the outer bract 
is not much longer than the inner 
one and only slightly longer than 
the inflorescence. 
The genus Sisyrinchium is com¬ 
monly called “ blue-eyed-grass.” 
ORCHID FAMILY (ORCHIDACEAE) 
The orchid flower consists of 3 sepals, 3 petals, 1 of which is very 
is a rather recent family in point of origin and has developed re¬ 
markable adaptations for cross pollination by means of insects. It 
cannot be said, however, to have developed along lines of greatest 
efficiency. In the first place the orchids have become ,so dependent 
upon insects that in most cases they cannot produce any seeds at all 
unless they are visited by certain of these small animals. In the 
second place, the seeds are extremely small and in most cases they 
will not germinate unless they are stimulated by the presence of 
certain kinds of fungi or by some artificial means such as a sugar 
solution. The result is that many kinds of orchids are exceedingly 
rare, except as they are cultivated and cared for by man. 
The orchid flower consists of 3 sepals, 3 petals, 1 of which is very 
different from the others and is called the lip, and a central column 
Figure 26.— Rocky Mountain iris. Light 
blue. Photograph by Geoffrey Coope. 
