Nov., 1907.] Life History of Cornus Florida. 197 



front slopes, and below them new flood plains. Most of the 

 terraces unless defended by rock ledges are subsequently cut 

 out, the flood plain is replaced by a new lower one, and gradually 

 but surely the old valley floor is more or less completely uncov- 

 ered and the old valley is restored similar to the form which was 

 filled by the accumulating sediments. 



The whole cycle of aggradation and degradation constitutes 

 but a little epicycle in the greater round of topographic evolution 

 to which the hard rock lands must submit — a little pleasure trip 

 which the stream takes while it rests from its great work of 

 baseleveling a region. So short-lived are the forms due to these 

 processes that the "eternal hills" do not change much during the 

 entire period of the terrace stage and many epicycles may come 

 and go and leave no record while one turn of the wheel of physi- 

 ographic development is being made. 



CONTRIBUTION TO THE LIFE HISTORY OF CORNUS 



FLORIDA.* 



William Clifford Morse. 



This study of the Flowering Dogwood was undertaken at the 

 suggestion of Professor John H. Schaffner and the first material 

 was collected September 26, 1905. When this material was 

 ready for study, it was found that the flower-buds for the next 

 year had already reached an advanced stage of development. 

 Microspores were already formed and the ovule Avas far developed. 

 Nevertheless, material was taken at intervals of a week during 

 the fall, monthly during the winter, and weekly again during the 

 spring. Through the kindness of Mr. Robert A. Young material 

 was collected, from June until September, 1906. during the 

 writer's absence from Columbus. To him the author takes this 

 opportunity of expressing his thanks. 



Schaftner's weaker chrom-acetic acid solution was empIoA'ed 

 as a killing fluid. Before placing the head of flower-buds in it, 

 however, the four bracts, which during the winter ai-e tightly 

 folded over them, and in the spring form the conspicuous invol- 

 ucure, were removed in order that the solution could better 

 penetrate the buds. Dehydrating and imbedding were per- 

 formed in the usual manner. Sections were cut from 8 to IS 

 microns in thickness. The vast majority, however, were 10 or 

 12 microns. Analin safranin was first used as a stain and after- 

 wards Delafield's Haematoxylin. The latter proved to be much 

 the better and the best results were obtained by overstaining and 

 then clearing for a long period in acid alcohol. 



* Contribution from the Botanical laboratory of the Ohio State University No. XXXI. 



