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 hypocotyl 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* has studied certain Araliaceae and Coulter and Cham- 

 berlain^ give a number of observations on Slum. By some the 

 Rubiales are regarded as close relatives of the XJmbellales. 

 Lloyd^ 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 an}^ 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., i oc, 1-12 obj. 

 Figs. 10-12, 18-21, B. & L., f oc, i obj. 

 Figs 22 and 23., B. & L., f oc, f 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. Julj^ 

 28, 190G. 



Fig. 5. Longitudinal section of a flower-bud, to show the growth of the 

 incipient ovule from the side of the stj^'ar 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 aie more or less connected as shown by 

 the dotted portion. January 29, 1906. 



Fig. 8. Section of microsporocyte with massed chromartin 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 laver. 

 September 26, 1905. 



1 Ducamp, L. Recherches sur I'embryogenie des Araliac^es. Ann. Sci. Nat. Bot. 

 VIII, 15. 311-402. pis. 6-13. 1902. 



2 Coulter, J. M. and Chamberlain, C. J. Morphology of Angiospenns. 1903. 



3 Lloyd, F. E. The Comparative Embrvologv of the Rubiar-eae BulL Torr. Bot. Club 

 28:1-25. pis. 1-3, 1899. Do. Mem. Torr. Bot. Club 8 : 27-112. pis, S-15. 1902. 



