SEED-BEARING PLANTS 
497 
The roughness of the surface is caused by the persistence 
of the styles and the fleshy sepals. 
The family is divided into several sub-families on the 
basis of various structural differences, such as phyllotaxy, 
venation of leaves, presence or absence of milky juice, 
presence or absence of perianth, and others. 
-FiG. 381. Cocoanut palms along the beach. Philippine Islands. 
(Photo from Bureau of Science, Manila.) 
432. Orchid Family (Orchidaceae). The Orchidaceae 
are the most highly developed of all monocotyledons. 
No flower surpasses the orchids in beauty of color- 
pattern, endless diversity of unusual forms, and wonder- 
ful mechanisms that secure cross-pollination by insects. 
As in the papilionaceous flower, the flower of orchids is 
bilaterally symmetrical (zygomorphic) , with (usually) 
three sepals resembling in texture the three petals (Fig. 
