1897 | THE LIFE HISTORY OF SAGITTARIA VARIABILIS 273 
FiG, 66. Embryo showing exceptional suspensor development; the cells 
below the vesicular cell have divided longitudinally. x 2 
Fig. 67. Embryo showing org of the stem apex by transverse division 
of a hypodermal cell in tier 6. X 26 
Fic. 68. Transverse section though the young cotyledon of an embryo 
at the same stage as fig. 67. X 400 
Fic, 69. Embryo showing ne differentiation in the re sas: of 
the stem tip by transverse division of the dermal cell. 2 
FiG. 70. Embryo a little older than jig. 69, ante the glandular 
appearance of the vesicular cell a. > 400. 
Fic. 71. Embryo showing further development of the cotyledon (c), stem 
apex (4), and hypocotyl (@). oO. 
FiG. 72. Embryo more advanced, with two susperisor cells below the 
vesicular cell. x 66 
Fic. 73. Section of mature ovule showing the position of the embryo, 
the cap of endosperm beyond the tip of the cotyledon, the fragments of the 
lower endosperm cells, and the original antipodal region projecting beyond 
the embryo sac somewhat like a vermiform appendix. 26. 
PLATE XXVI. 
Fig. 74. Part of an embryo, iggeis the beginning of the differentiation 
of the teh of the root. X 216 
G. 75. tas tip of an See showing a espana with more than five 
ay « S 
FIG. Ome aon of the root tip of an embryo showing the differentiation 
of a single hypodermal cell into an initial cell. >< 216. 
FiG. 77. Section of root tip showing the distinct differentiation of derma- 
togen, periblem, plerome, and calyptrogen, and also the initial cell. 216. 
Fig. 78. Section of a root tip about the same stage as fig. 77, but with 
less regularity in the arrangement of the cells. >< 216. 
FiG. 79. Section of the root tip of a nearly mature eetides ne the 
arrangement of the tissues. < 216. 
Fic. 80. Transverse section through the apex of the root of a mature 
embryo, showing the single initial cell at the growing point. X 216. 
Fig. 81. Transverse section a little beyond that shown in fg. §0, show- 
ing differentiation of the plerome cylinder. X 216. 
Fig. 82. Transverse section through the hypocotyl, eee the arrange- 
ment of the dermatogen, periblem, and plerome. X 216. 
Fié. 83. Longitudinal section through the apex of the stem in a mature 
xX 140. 
