20 BOTANICAL GAZETTE [JANUARY 
Salix sericea.—Leaf: upper epidermal cells small, strongly 
cuticularized; mesophyll compact, palisade of two layers of long 
narrow cells; stomata on under surface, guard cells sunken beneath 
the slightly protuberant companion cells; hypoderma of five- or 
six-cell-layers on hadrome side, and eight layers on leptome side of 
midvein. Root: resinous bodies present in medullary rays and 
cortex, the latter consisting of thick-walled cells; no mycorhiza. 
Ledum_ groenlandicum.—Leaj: upper epidermis rugose, with 
scattered unicellular hairs, margins strongly revolute, cuticle present, 
cell walls thickened, the radial walls being broadly undulate; lower 
epidermis covered with a thick cuticle and a felt of long multicellular 
and short unicellular hairs, glandular hairs usually present near the 
small veins, stomata protuberant; palisade of three or four layers 
of broadly oblong cells; beneath vascular tissue of midvein and 
between the mestome bundles occur large air.cells which may form 
lysigenic air cavities in the older leaves. Root: mycorhizal. 
Larix laricina—Leaf: bifacial, deciduous; epidermis thick- 
walled, slightly cuticularized, guard cells sunken beneath the com- 
panion cells; palisade tissue developed toward the dorsal surface, 
two layers thick showing a radial tendency, stereome reduced to a 
few cells beneath the leptome; two resin ducts near edges of leaf. 
Root: composed of mycorhiza, resinous deposits throughout, cortical 
tissues early destroyed by fungus. When grown in culture solutions 
and well aerated, normal roots with root hairs are produced. 
Picea Mariana.—Plants in bogs are stunted. Leaj: epidermal 
cells thick-walled, cuticle present, guard cells sunk beneath the 
companion cells; mesophyll cells compact, of a more or less radial 
palisade type. Root: mycorhizal, resin deposits throughout, cortical 
tissues destroyed by ieee Normal roots are developed under 
culture conditions. 
Pinus Strobus.—Plants very much stunted-in the bogs, leaves 
shorter and thicker. Leaj, epidermal walls so greatly thickened 
that scarcely a lumen remains, beneath this a hypodermal layer of 
thick-walled cells; mesophyll cells compact and of the usual lobate 
type. Root: mycorhizal, cortical tissues traversed by the fungus 
hyphae; resinous deposits throughout. Stem: annual rings narrow 
