250 PLANT ORGANS AND PARTS OF PLANTS. COMPARISON OF PEA, BEAN, AND LENTIL. Palisade Epi- dermis. Hypodermis. Parenchyma OF Cotyle- dons. Starch. Pea . . .
to no microns
long (average 90), not conical toward cuticle ; inner cell wall ir- regular ; lumen wide near the in- ner wall, con- tracting in cen- tre, and widen- ing externally. Delicate goblet, beaker or dumb- bell-shaped cells whose inner walls are somewhat thicker than outer ; large intercellular spaces between cells at side (radial diameter 30 to 36 microns, transverse 36 to 45 microns), rather thick walls with cleft pores, no crystals. Moderately thick -walled cells, 3 mi- crons, pit- ted ; cell wall smooth or minutely beaded in cross-section.
to 51 microns, ir-
regular in shape, with many pro- tuberances ; reni- form and bean- shaped forms, few elliptical. Hilum in many absent as fissure ; distinctly annulated. Bean . .
to 60 microns
long ; not conical at cuticle ; wall smooth within ; lumen wide at in- ner side, occlud- ed soon to peri- phery. Cross-section four- sided, without in- tercellular spaces (radial diameter 15 to 30 microns, trans- verse 15 to 25 mi- crons), thickened at the sides and containing crystals of calcium oxalate (6 microns). Thick-walled cells with large pores, walls at least 5 microns thick and coarsely beaded in cross-section. Distinctly elliptical, up to 57 microtis ; kidney- and bean- shaped with long cleft hilum. An- nulations marked. Lentil .
microns long,
with a short coni- cal projection at cuticle ; inner wall smooth; lu- men wide, con- tracting toward outer wall. Compressed dumb- bell or hourglass- shaped, often ir- regular, seldom elongated, with in- tercellular spaces and cleft pores (ra- dial diametef 9 to 24 microns, mostly 15 to 18 microns; transverse diam- eter 15 to 30 mi- crons), no crystals. Thin-walled cells which on cross-sec- tion are slightly or indistinctly pitted.
to 45 microns, re-
sembling both bean and pea grains ; many with concen- tric markings, not as distinct as bean starch ; many with small unbranched fissured hilum, others no fissure.
filled with starch grains. The starch grains are very irregular, but are elongated oval, with lacerate elongated hilum. They average 20 to 40 microns in short and long diameters.
The seed of the bean resembles that of the pea very closely, but differs in a few important particulars. The epidermal cells are palisade-like, as in the pea, but the thickening of the cell walls is very characteristic. The entire lumen of the epidermal cells is occluded save at the base, where the walls become thinner. The palisade cells are also shorter (30 by 60 microns). The hypoderm
