308 PHARMACEUTICAL BOTANY 
1. Epicarp or epidermis consisting of a layer of thick- 
walled epidermal cells whose outer walls show the presence of a 
thin yellow cuticle. Stomata are present in this tissue. The 
epidermal cells contain protoplasm and brownish bodies. Some 
also contain small prisms of calcium oxalate and a few vanillin 
crystals. 
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Fic. 233.—Vanilla. Structure of the capsular fruit. ¢, cuticle; ¢p, epidermis; 
hy, hypodermis; mes, mesocarp of parenchyma in which region fibrovascular bundles 
(4) course; ir, tracheae, si, sieve tissue and J, sclerenchyma fibérs of a bundle; end, 
endocarp; f/, placenta; h, glandular hairs; sd, seed; s, suture; cr’, prismatic crystals 
and cr?, raphides of calcium oxalate. 
2. MesocarpP, a broad region divisible into a narrow, outer 
hypodermis and broad inner parenchyma zone. The hypo- 
dermis is composed of one to several layers of collenchymatic 
cells with dark-colored contents. Its cells are somewhat larger 
than those of the epidermis and thicker-walled. The inner 
parenchyma zone is composed of somewhat loosely arranged, 
large, thin-walled parenchyma cells becoming smaller in the 
inner part of this region. Most of these cells contain brownish 
contents but some possess long raphides of calcium oxalate. If 
the section be mounted in phloroglucin solution (5 per cent.) and 
