The Morphology and Relationships of Circaeaster

The present morphological study of Circucastcr agrestis Maxim, was initiated because this plant is another example, in addition to Kingdonia. of an angiosperm with open rlicholum.n-\.-i.i'i«m.This type of foliar vasculature is extremely iare in tl ■ diioti l-'di ind \. -< i< mi and phylogenetic significance raises vei nil • »lems which have recently been discussed in detail (Foster 1959(Foster , 1961a(Foster , 1961b;; Foster & Arnott 1960).Throughout the long and vexed taxonomic history of Circaeaster, little attention has been given to its dichotomous venation and no attempt has been made to study possible fluctuations in the details of this pattern or to determine the existence of anastomoses or blind veinendings.It is believed that the present study, based on the comparison of a wide range of 1< il m iterial give ; fairlj accurate picture of the trends of variation and demonstrates the often remarkable symmetry of the 1963]