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EXPLANATION OF PLATES XXVITI-XXXI 
Fics. 1-6.—Successive stages in germination of seeds of Balsamorrhiza 
sagittata: fig. 1, seed coat bursting, with hypocotyl protruding, 15 days’ 
growth; figs. 2-5, stages from 20 to 4o days’ growth; fig. 6, stage showing 
60 days’ growth; note type of venation in plumule; figs. 1-5, X1.5; fig. 6, X1I- 
| Fics. 7-10.—Successive stages in development of bundle anatomy of 
seedlings: fig. 7, formation of protoxylem, other tissues yet undifferentiated; 
fig. 8, protoxylem (px) well defined, rapid differentiation of procambium ($c) 
in region where protophloem originates; fig. 9, rapid division of cambium to 
form secondary xylem elements (mx) and phloem (ph); fig. 10, suberization 
of endodermis (em) beginning, secondary xylem, the metaxylem, well differen- 
tiated; X112. 
Fic. 11.—Gradation of tracheids from spiral protoxylem to true eyelet 
type of eg taken in region of fig. 10; X150. 
Fic. 12.—Detail of suberized walls in region of endodermis, defining “H” 
type of ckening: ex, toward cortex; in, toward leptome. 
Fic. 13.—Section through 10 mm. root, illustrating passage of phloem 
strands through endodermis into cortex in region of canals: ph, phloem cells; 
rc, resin canals; bf, strands of bast fibers; cx, cells of cortex; st, suberized 
thickening of endodermis; 150 
Fic. 14.—Diagram of resin canals in longitudinal section through stout 
rootstock and root branches: 7,, outer series of canals; r2, inner series of 
canals; r;, anastomosing radial connections; note inner series ends in stele 
just above tap root; 0.75 
Fic. 15.—Transverse section through old root: r:, outer series of canals; 
r2, inner series of canals; r;, radial connections; sch, sclerome groups; /1, ha, 
lysigenous splittings of rays; 150. 
Fic. 16.—Section through young subsidiary root with stele yet unsclerified, 
showing bundle anatomy: px, protoxylem; cx, cortex; hyp, hypodermis; 
é, epidermis; note deposits of inulin in granular masses; type of root readily 
permeable to alcohol; 150. 
Fic. 17.—Section through subsidiary root with moderate thickenings; 
note suberization of endodermis, rapid division of cambium, metaxylem ele- 
