256 Campbell. — Contributions to the 
Figs. 27 and 28. Longitudinal sections of embryos in which the ligule (x) is 
beginning to form. Z, leaf ; r, root, x 300. 
Fig. 29. Four transverse sections of a young embryo, a, nearest the arche- 
gonium ; d, furthest from it ; II II, the quadrant wall, x 300. 
Fig. 30. A median section of a somewhat older embryo than 28. b , section 
of the root of the same, x 300. 
Figs. 31-35. Five vertical sections (at right angles to the longer axis) of an 
embryo of about the same age as Fig. 30. Fig. 31 is a median section/ the others 
through the root, x, the ligule. x 300. 
Figs. 36-38. Three horizontal sections of a somewhat older embryo ; letters as 
in the other figures, x 300. 
Fig. 39. Median longitudinal section of an older embryo, x 300. r, root ; 
L, leaf; p, foot; x, ligule; v, sheath. 
PLATE XVII. 
Fig. 40. Section of the prothallium, with the contained embryo (em). X125. 
ar, archegonia ; sp, spore-membrane. 
Fig. 41. Outline of an embryo at the time of formation of the second leaf (Z 2 ), 
X125. 
Figs. 42, 43. Two longitudinal sections of the first leaf of an advanced embryo. 
X300. 
Fig. 44. Longitudinal section of the root of a similar embryo, x 300. 
Fig. 45. Apical region of the stem (si) of the embryo shown in Fig. 41. Z 1 , 
Z 2 , first and second leaves ; r, root ; x l , ligule of first leaf ; v, sheath, x 300. 
Fig. 46. Similar section of a young plant in which the first leaf was nearly full- 
grown. Letters as before, x 300. r 2 , rudiment of the second root. 
Fig. 47. Section of a somewhat younger plant than that shown in Fig. 46, 
showing the first rudiment of the second root (r 1 ). Z 2 , the second leaf, x 300. 
Fig. 48. Longitudinal section of the young second leaf (Z 2 ) cutting through the 
second root (r 1 ). The tracheides have already formed at the base of the first 
root, x 300. 
Fig. 49. Cross-section near the base of the first leaf of the young plant, showing 
the intercellular spaces (?) and the second leaf (Z 2 ) and ligule (x) surrounded by 
the sheath (v) at the base of the leaf, x 300. 
Fig. 50. Median longitudinal section of a young plant with two full-grown 
leaves. X125. Pr, Prothallium ; P r 2 , roots; Z 1 , Z 2 , Z 3 , leaves; si, stem; 
sp, spore-membrane ; ar, archegonium neck. 
