“TES ips oer ‘ 
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Te ee Pe Oe Tek ee a a ee eee he 
é aes iin pada 3 
1898 | EMBRYOLOGY OF ALYSSUM 323 
7. The first and second series of divisions in the terminal 
embryo cell are longitudinal and form a quadrant. The octant 
is formed by a series of transverse divisions. 
8. The first three series of divisions in the basal embryo cell 
correspond to those of the terminal embryo cell, also giving 
rise to an octant. 
9. The dermatogen is the first tissue which is differentiated 
and is cut off by tangential walls in the cells of the octants. 
10. The plerome and periblem arise in the basal hemisphere 
of the terminal embryo cells; the cotyledons and stem tip from 
the terminal hemisphere. 
11. The calyptrogen and root cap are formed from the basal 
hemisphere of the basal suspensor cell, while that part of the 
root tip which forms the periblem of the radicle arises from the 
hemisphere lying next to the terminal embryo cells. 
12. The number of cells in the suspensor varies from six to 
fifteen. The number beyond six apparently depends upon the 
number of intercalary divisions, some of which may be longi- 
tudinal. 
13. The endosperm lines the entire embryo sac with a single 
layer of cells, but is more abundant around the young embryo 
and forms a peculiar growth in the ancpede region. 
Cotumus, OHIO. 
EXPLANATION OF PLATES XXVI-XXVIII. 
Drawings redyced to three-eighths; the magnification given with each 
figure refers to the original magnification before reduction. 
PLATE XXV1, 
Fic. 1. Nucellus and integuments ; archesporial cells. X 1060. 
Fic. 2. Nucellus with tapetal cell, 4; potential macrospores, #; and vital 
Macrospore, 7. 1060 
FIG. 3. Two-celled embryo sac; tapetal cell, 4. X1060. 
Figs. 4-5. Four-celled embryo sac. X 1060. 
Fic. 6. Eight-celled embryo sac. ae 
Fic. 7. Seven-celled embryo sac. X10 
Fic. 8. Egg apparatus and definitive ae xX 580. 
Fics. 9 and 9a Embryo sac — fertilization ; antipodals, a. X 1060. 
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