DEVELOPMENT OF SEED IN POLYGONACEAE 
475 
EXPLANATION OF PLATES XLV-XLVIII 
All figures drawn from median longitudinal sections, except figures 8, 9, 10, 
13, 19, 21, and 26, which are from cross-sections. The following abbreviations are 
used: A, aleurone layer; C, cotyledons; CA, embryonic cells of endosperm; CY, 
cavity left by shriveled suspensor; D, depleted portion of aleurone layer; D', remains 
of micropylar portion of integuments and nutritive layer; E, embryo; EN, endo- 
sperm; F, remains of suspensor; H, haustorium-like structure; HY, hypocotyl; /, 
integuments; K, embryo sac; L, enlarged aleurone layer; N, nucellus; N' , remains 
of undifferentiated nucellus; NU, "nutritive jacket"; 0, mature seed coat; OT,. 
mature seed coat plus remains of integuments; P, plumule; R, radicle; SH, sheath- 
like structure; T, suspensor. 
Fig. I. Polygonum Persicaria, showing the embryo in the octant stage and the- 
endosperm in the free nuclear condition; X 53. 
Fig. 2. P. Persicaria. The embryo showing the first differentiation of the- 
cotyledons; the upper portion of the endosperm has become cellular, while no cell 
walls have appeared in the lower portion; haustorium-like structure evident at the 
base of the embryo sac; X 40. 
Fig. 2a. Portion of longitudinal section of P. Persicaria seed at about the stage 
shown in fig. 2; only the outermost layer of the nucellus, the "nutritive jacket," 
remains functional; the endosperm shows an outermost layer of embryonic cells and 
a more central region of large vacuolate cells; X 248. 
Fig. 3. P. Persicaria. A later stage in which the embryo sac has become com- 
pletely filled with c( llular endosperm, except at the base where the haustorium-like 
structure is seen; embryo at the side; X 31. 
Fig. 4. P. Persicaria. Mature seed; endosperm filled with starch; aleurone 
layer present; nucellar tissue practically all obliterated; embryo at the side; dotted 
line indicates plane of cross section shown in fig. 9; X 31. 
Fig. 5. Polygonum aviculare. Mature seed; aleurone layer present; endo- 
sperm filled with starch; embryo with well developed plumule at the side of the 
seed; nucellar tissue nearly obliterated; dotted line indicates plane of cross section 
shown in fig. 8; X 31. 
Fig. 6. Polygonum Convolvulus, showing embryo in the octant stage and the 
endosperm in the free nuclear condition; X 64. 
Fig. 7. P. Convolvulus. Mature seed; aleurone layer and starch filled cellular 
endosperm present; embryo at the side; nucellar tissue practically obliterated; 
dotted line indicates plane of cross section shown in fig. 10; X 20. 
Figs. 8-10. Fig. 8. Polygonum aviculare; fig. 9, P. Persicaria; fig. 10, P. 
Convolvulus; showing the relative position of the cotyledons in the three species; 
dotted lines indicate plane of longitudinal sections shown in figs. 4, 5, and 7; X 14. 
Fig. II. Rumex crispus. Mature seed; aleurone layer and starchy endosperm 
present; embryo at side of seed; nucellar tissue practically obliterated; dotted line 
indicates plane of cross section shown in fig. 13; X 31. 
Fig. 12. Rumex Acetosella. Mature seed; starchy endosperm and aleurone 
layer present; embryo at side of seed; nucellus nearly obliterated; X 42. 
Fig. 13. Rumex crispus. Cross section of mature seed showing position of 
cotyledons; dotted line indicates plane of longitudinal ssction shown in fig. 1 1 ; X 14. 
