124 PHARMACEUTICAL BOTANY 
to give off watery vapor (transpiration) and take in or give off 
carbon dioxide, and oxygen. In addition to stomata some 
leaves possess groups of water stomata which differ from the 
ordinary or transpiration stomata in that they always remain open, 
are circular in outline, give off water in droplets directly, and 
lie over an area of small, secreting, glandular cells (epithem) 
which is in connection with a bundle of tracheids that springs 
from the end of one or more fibro- 
vascular bundles. An air chamber usu- 
ally occurs directly beneath the water 
pore. Haberlandt gave the name of hyda- 
thode to this and related types of structures 
which secrete water in the form of drop- 
lets. Examples: Leaves of Primula, 
Corn, various grasses, Potato, Elm, Lark- 
spur, Crassula, Saxifraga and Ficus. 
EpmERMAL AppEeNDAGES.—The epi- 
Fic. 65,—Radial-longi- Germis of leaves, stems, fruits, and seeds 
tudinal section through a Of many plants frequently gives rise to 
hydathode from the leaf oyt-growths in the form of papilla, hairs 
margin of Primula sinensis. d ] 
i, upper, and j, lower epi- sspeae -nabinge 
dermis; h, palisade cell; ¢, EPIDERMAL Papi_L@ are short pro- 
thin walled parenchyma tuberances of epidermal cells. “They may 
eset reusnd be seen to advantage on the upper epi- 
water stoma; &, tracheids, Germis of the ligulate corolla of various 
(From Stevens, after Haber- species of Chrysanthemum, on the lower epi- 
londt.) dermis of the foliage leaves of species of 
Erythroxylon and upon the upper epidermis of the petals of the 
Pansy (Viola tricolor). EpmpERMAL Hairs or TRICHOMES are more 
elongated outgrowths of one or more epidermal cells. “They may 
be unicellular, as those of the seed of cotton, or multicellular, non- 
glandular (simple) or glandular. The non-glandular hairs may 
be of various shapes, viz.: clavate (club-shaped) as on Rhus 
glabra fruits; stellate (or star-shaped) as on Deutzia leaves; 
candelabra-shaped, as on Mullein leaves; filiform, as on Hyoscy- 
amus, Belladonna and Digitalis leaves; hooked, as on the stems 
of the Scarlet Runner or Hops; barbed, as on the stems of Loasa 
species; or tufted, as found on the leaves of Horehound (Marru- 
