June, 1907.] 
Life History of Cornus Florida. 
203 
A complete embryo was taken from a seed of August 11th. 
The cotyledons had become much expanded, were much broader 
than the hypoeotyl or stem, and about the same in length. 
So far as the writer’s knowledge goes very little special work 
has been done on the Cornaceae. Among the related forms, 
Ducamp 1 has studied certain Araliaceae and Coulter ajid Cham¬ 
berlain 2 give a number of observations on Sium. By some the 
Rubiales are regarded as close relatives of the Umbellales. 
Lloyd 3 has made extensive studies on the embryology of this 
order; but until we have a more detailed knowledge of the. 
related groups it would be useless to make any generalization 
from the present study of Cornus. 
The writer wishes, in closing, to express his thanks to Pro¬ 
fessor Schaffner who has gone over all the work and given much 
needed advice and criticism. 
Explanation of Plate XIV. 
The drawings were outlined with the aid of a camera lucida, and the 
following optical combinations were used: 
Figs. 1-7, B. & L., 2 oc., § obj. 
Figs. 8 and 9, 13—17, B. & L., £ oc., 1-12 obi. 
Figs. 10-12, 18-21, B. & L., $ oc., £ obj. 
Figs 22 and 23., B. & L., J oc., 5 obj. 
Fig. 1 . Longitudinal section of young flower-bud, showing two of the 
four incipient sepals. July 21, 1906. 
Fig. 2 . Longitudinal section of a somewhat older flower-bud of the 
same head, showing the incipient petals. 
Fig. 3. Longitudinal section of a still older flower of the same head, 
showing, besides the growing sepals and petals, two of the 
four incipient stamens. 
Fig. 4. Longitudinal section of a flower-bud, to show the growth of the 
ring-like ridge to form the stylar canal of the carpel. July 
28, 1906. 
Fig. 5. Longitudinal section of a flower-bud, to show the growth of the 
incipient ovule from the side of the stvlar canal. August 
11 , 1906. 
Fig. 6 . Longitudinal section of a flower-bud, to show the curving of the 
lower fourth of the stylar canal around the ovule at right 
angles to the curvature of the ovule. August 18, 1906. 
Fig. 7. A somewhat diagramatic longitudinal section of a flower, show¬ 
ing the four sets of organs in position. The two ovules lie in 
two parallel planes at right angles to the rest of the drawing. 
The two stylar canals are more or less connected as shown by 
the dotted portion. January 29, 1906. 
Fig. 8 . Section of inicrosporocyte with massed chromatin and large 
free nucleolus. August 26, 1906. 
Fig. 9. Section of a microspore tetrad. August 26, 1906. 
Fig. 10. Longitudinal section of part of an anther, showing the epider¬ 
mis, endothecium, parietal layers, and broken tapetal layer. 
September 26, 1905. 
1 Ducamp, L. Recherches sur l'embrvogenie des Araliacfies. Ann. Sci. Nat. Bot. 
VIII, 15. 311-402. pis. 6-13. 1902. 
2 Coulter, J. M. and Chamberlain, C. J. Morphology of Angiosperms. 1903. 
3 Lloyd, F. E. The Comparative Embryology of the Rubiareae Bull. Torr. Bot. Club 
2S : 1-25. pis. 1-3, 1899. Do. Mem. Torr. Bot. Club S : 27-112. pis. 8-15. 1902. 
