THE STUDY OF THE EVOLUTION 



W 



261 



4. CORNACEiE. 



Nine g 



of Cornaceae have been studied 



Cornus^ Marlea, Aucuha, Garry 



Helwingia, Corokia, Melanophylla, Griselinia, and Ny 



Eacli genus is described separately, and the points are taken in the following 



der : — 



Morphology of the flower and ovule 

 Vascular structure. 

 Interpretations and comparisons. 



{a) ConNUS. 



flo 



ith 



fer 



Morphology of the Mower and Ovule. 



The genus Cornus was made the type of a new family, the Cornese, by De Candolle 

 and is characterized by possessing polypetalous, epi 

 bilocular ovary (rarely trilocular, according to Bentham and Hooker), surmounted 

 by alternating tetramerous whorls of sepals, petals, and stamens. The genus Benthamia, 

 established by Lindleyf in 1833, which produces flowers of the Coriius type grouped to 

 form a globular capitulum, is now regarded as a subgenus of Cornus, since the kind of 



inflorescence no longer forms a distinctive character. 



The writer has devoted special attention to the following points : — Variability in the 

 ovary, the 

 nucellus. 



structure of the style, the insertion of the ovules, and the structure of the 



The flowers of several species of Cornus, including C. mas, C sanguinea, C. Amommn, 

 C. alba, have been examined, but the ovaries have proved to be bilocular without 

 exception. Benjamin Clarke I, however, records that he found several loculi in cultivated 

 specimens of C. sanguinea. Thus he states :— " I have found, when cultivated in a nursery, 

 tlie number of petals and stamens frequently increased to five, six, seven, or more — the 

 greatest increase observed being eight petals and ten 



bein 



stamens, the ovary of the flower 

 four-celled; the carpels, however, sometimes increased to seven witliout any 



further increase of the petals and stamens." 

 The ovary of Cornus, which is 



terminated by a single style, 



might not be 



strictly bicarpellary, for several instances have been recorded in other families 

 where the loculi and the styles present in the ovary belong to different carpels. 



of the styles of four carpels. Now the 



Or 



again, the style might be composed 



structure of the style in C 



mas 



does not afford a clue as to its composition 



The 



stylar canal is ribbon-shaped and opens out eventually into the loculi. Clarke, however, 

 observed important structural peculiarities in the styles of C. alba and C. sanguinea. 

 He found that the canal in the upper part of the style is four-lobed— the lobes 







Be Candolle, Prodromus, iv. 271. 



B. Clarke in Hooker's Kew Joavn, Bot. ii. (1850) 130. 



t J. Linuley in Bot. Keg. t. 1579. 



