HAZEN: TRIMORPHISM AND INSECT VISITORS OF PONTEDERIA 465 
them is unsafe, since Willstátter finds that in Centaurea and some 
other plants purple, red, or blue anthocyanin may readily change 
to a colorless isomer. These large cells were first noticed in ma- 
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Fics. 2-5. 2. Outer surface of sepal-segment: showing stomata in the epi- 
dermal layer; large subepidermal idioblasts shaded with broken lines, and three 
raphide-sacs (r.) in tbe same layer; the mid-vein (m.v.) and a lateral vein (/.2.) 
lying underneath; on the surface, hairs of two forms ( X I05). 3. Typical simple 
glandular hairs on the lower part of the perianth tube (X 105). 4. Hairs near tip 
of filament of mid-length stamen (X 113). 5. Cross section of filament from a bud 
3 mm. long; showing a raphide-sac, and several of the elongated hypodermal idio- 
blasts shaded ( X 113). 
