78 
ADA HAYDEN 
Epidermis of uniformly thin-walled cells; mostly oblong, slightly hairy on upper 
surface; longer hairs on lower surface; an occasional glandular trichome on 
upper surface; epidermis dips down into the palisade in folds at intervals. 
, Palisade parenchyma loose; large-celled. 
Vascular bundle surrounded by large cells, apparently water reservoirs. 
Summary: Photosynthetic tissue prominent; the thin-walled epidermis contrasts with 
the fairly numerous trichomes on both surfaces and with the presence of water 
reservoirs. 
Artemisia ludoviciana Nutt. 
Habitat: Dry slopes. 
Orientation and arrangement: Horizontal to ascending; alternate. 
Gross structure: Lanceolate; upper mostly entire; lower cut-lobed, toothed, or pinnati- 
fid; whitened woolly. 
Histology: Bifacial (fig. 24, plate XHI). 
Epidermal cells variable in size; thickness of walls variable, not much thicker on 
the outside than on the inside; trichomes numerous on both sides, but most on 
the upper side of leaf. 
Stomata small, not much depressed. 
Palisade parenchyma 2 layers, occupying 1/3 of the parenchyma space; large- 
celled. 
Spongy parenchyma, cells large; rather loose. 
Summary: Epidermal tissue not well developed except with regard to trichomes* 
• photosynthetic tissue prominent. 
Aster salicif alius Ait. 
Habitat: Alluvial basin; low land; moist soil. 
Orientation and arrangement: Horizontal to ascending; opposite; sessile. 
Gross structure: Linear to linear-oblong; glabrous, sometimes scabrous. 
Histology: Centric (fig. 17, plate XH). 
Outer walls of epidermis about 3 times as thick as inside walls. 
Stomata on both sides. 
Palisade parenchyma, 2 layers on upper, i layer on lower side; occupies about 2/3 
the parenchyma space. Cells medium-sized. 
Spongy parenchyma, cells large; fairly compact. 
Summary: Epidermis with fairly well developed cuticle though with stomata on both 
sides; photosynthetic tissue prominent. 
Coreopsis palmata Nutt. 
Habitat: Prairie slopes; dry to moist. 
Orientation and arrangement: Ascending; sessile; opposite. 
Gross structure: Wedge shaped; lobes broadly linear; glabrous. 
Histology: Centric (fig. 20, plate XII). 
Epidermis of small oblong cells; the outer walls thickened, 2 to 3 times the thick- 
ness of inner ones. 
Palisade parenchyma occupies 2/3 of parenchyma space; 3 layers above, 2 layers 
below. 
Spongy parenchyma, cells large but fairly compact. 
Resin ducts present. 
Summary: Outer wall of epidermis fairly well developed; photosynthetic tissue promi- 
nent. 
Helianthus tuber osus L. 
Habitat: Slopes and level; dry to moist soil. 
Orientation and arrangement: Horizontal; alternate. 
Gross structure: Oblong-lanceolate; scabrous above, pubescent below. 
