the Seed in the Alsinoideae. 
55 
Fig. 23. Spergula arvensis. Transverse section of ovule showing embryo-sac cut through the 
cotyledonary and hypo-cotyledonary portion, the proliferation of layer 2 of the outer integument, 
forming a wing of tissue round the ovule in the plane of the embryo, and secondary club-shaped 
papillae on the cell-walls of layer 1 of the outer integument : w. wing ; other lettering as before, 
x 110. 
Fig. 24. Cerastium perfoliatum. Longitudinal section of germinating seed, showing elongation 
of cotyledons ; h. hilum ; other lettering as before, x no. 
Fig. 25. Cerastium perfoliatum. Transverse section of germinating seed, same stage as Fig. 24, 
cut through the apex of embryo and nucellus in the root-cap region of the former, showing the 
sequence of tissues and their relation to the endosperm cap : Testa : 0. i. outer integument ; i. i. inner 
integument (two layers fused) ; per. 1. peripheral layer of nucellus ; end. c. endosperm cap ; Embryo : 
r. c. root cap; c. cortical layers, outer densely packed with starch contents ; pc. s. procambial stand, 
x 450 - 
Fig. 26. Cerastium perfoliatum. Transverse section of germinating seed ; same series as Fig. 
25, just above root cap ; lettering as before, x 450. 
Fig. 27. Cerastium perfoliatum. Diagram of transverse section of germinating seed showing 
the radicle of the embryo surrounded by the endosperm cap. x no. 
Fig. 28. Cerastium perfoliatum. Transverse section of germinating seed, same series, through 
hypocotyl of embryo, above the endosperm cap ; lettering as before. X 450. 
Fig. 29. Spergula arvensis. Longitudinal section through germinating seed, showing spiral 
elongation of cotyledons, extrusion of hypocotyl and subsequent rupture of endosperm cap, with 
axile cells of nucellus reduced to a few strands : hyp. hypocotyl ; other lettering as before, x 75. 
Fig. 30. Spergula arvensis. Same section, cells of endosperm cap under higher magnification, 
showing small quadrate cuticularized cells of layer 2 of the inner integument, which are only so 
modified in the apical region of the ovule in this species; lettering as before, x 450. 
Figs. 31-34 are from seed which was three years old. Where the endosperm cap extruded 
slightly through the micropyle (Fig. 31, end. el) the exposed cells had dried up and this portion 
formed a dark mark on the endosperm cap (Fig. 33, end. cl) which was observed on all these seeds. 
Figs. 31-34. Spergularia salina. Germinating seed from the first extrusion to the rupture of the 
endosperm cap by the elongating radicle of the embryo to the formation of root hairs on the latter : 
pap. papillae ( formed by outgrowth of some cells of layer 1, outer integument') ; w. wing; end. c. 
endosperm cap ; r. h. root hairs; r. c. root cap ; sth. statolithic starch ; hyp. hypocotyl. x 75- 
Fig. 35. Spergula arvensis. Seedling, cotyledons extruded, the endosperm cap remaining on the 
seed- coat: cots, cotyledons; r. h. root hairs; end. c. endosperm cap, mag. 
Fig. 36. Stellaria Holostea. Longitudinal section showing two megaspores in one nucellus : 
m. megaspore ; ax. c. axile cells ; epi. epidermis; ap. nuc. apex of nucellus. x 1100. 
Fig. 37. Sagina procumbens. Longitudinal section of ovule showing vegetative outgrowth 
of nucellus : nuc. nucellus. 
Fig. 38. Sagina procumbens. Apex of cotyledon just emerging from seed coat : epi. epidermis ; 
tra . tracheids. 
Fig. 38 a. Tracheids. x 450. 
Fig. 38 b. Longitudinal section of cells of the epidermis with starch contents : st. starch ; cut. 
cuticle, x 450. 
F'ig. 39. Surface view of stoma on ventral surface of cotyledons just emerged from seed coat : 
sto. stoma, x 450. 
Fig. 40. Surface view of a water stoma surrounded by loose epithem cells, on dorsal surface of 
cotyledon, just emerged from seed coat, x 450. 
