558 SmitH: DIosCcOREA VILLOSA 
Description of plates 31-34 
With the exception of Fic. 28, all drawings were made with an Abbé camera 
lucida, the drawing being at the level of the base of the microscope. Leitz oculars 
and objectives were used: Fic. 1, ocular III and ee 7; Fies. 2-09, ocular III 
and objective 1/16; Fics. ro-12, ocular I and objec'ive 7; Frc. 13, ocular I and 
objective 3; Fics. 14-24, ocular I and objective 4; Fics. 25-27, ocular I and objec- 
tive 6. The drawings have been reduced one fourth in iepeaaaes on. 
PLATE 31 
1. Mature embryo-sac. 
2. Two-celled embryo. 
3. Three-celled Scaa 
Fic. 4. Four-celled embry 
5. Four-celled ered with one of the terminal cells in mitosis. 
6 
. 9. Embryo somewhat older theti those shown in Fics. 7 and 8; region 
in Wb cell division “ie become especially active, 
Fic. 10. Ider embryo in which suspensor and Shay have become differentiated 
and which shows he first indication of the development of the primordium of the 
first secondary leaf, /; suspensor, s. 
Still older embryo in which the first secondary leaf, J, has begun 
development. The section was cut somewhat obliquely so that not all of the sus- 
pensor is shown; cotyledon, c. 
PLATE 32 
Fic. 12. Median longitudinal section through the ese gsa embryo» 
showing first secondary leaf, 1, and the growing point of the ste 
IG. 13. Surface view of the full-grown embryo; neu s; first secondary 
leaf, 1; cotyledon, c. 
Fics. 14-21. Series of outlines, ea on the same scale, of median longitudinal 
sections of embryos, showing the d pment of the mature organs; first secondary 
leaf, 1; cotyledon, c 
PLATE 33 
Fics. vibe Continuation of the preceding series, Fic. 24 showing the full- 
grown embry 
Fic. 25. ese is through the primary root of the seedling; cotyledonary 
trace, ¢. 
PLATE 34 
Fic. 26. Cross-section through the n Gone of the seedling; cotyledonary 
trace, t; traces from the first secondary lea 
Fic. 27. Cross-section through the of the petiole of the cotyledon. 
FIG. 28. Seedling dissected out of the seed; first secondary leaf, 1; cotyledon, ¢ 
