Transitional Herbaceous Dicotyledons . 1 
BY 
EDWARD CHARLES JEFFREY, 
Harvard University , 
AND 
RAY ETHAN TORREY, 
Massachusetts Agriculttiral College. 
•» 
With Plates XI-XIII and five Figures in the Text. 
A NUMBER of years ago, in one of the contributions issuing from this 
laboratory, Eames (1) described the origin of the herbaceous type in 
the Dicotyledons with special reference to the Rosaceae. The conclusions 
reached by this author vouched for the appearance of the herbaceous 
condition as the result of the formation of large storage rays in relation to 
the entering foliar traces. The evidence presented clearly indicates the 
derivation of these large foliar storage rays from the union of what were 
originally aggregations of more or less modified ordinary rays in proximity 
to the leaf-strands. In the midst of these aggregations of rays the vessels 
become transformed first to fibres and later, together with other originally 
elongated elements, into parenchyma. The parenchyma originating from the 
transverse septation of longitudinal prosenchyma becomes more and more 
assimilated with the radial parenchyma in its dimensions, and in extreme 
cases is scarcely distinguishable from it. It is clear, if the method of 
origin of foliar ray described by Eames for herbaceous representatives of the 
Rosaceae is correct, that herbaceous forms are derived from woody or 
arboreal ancestors. More recently, two authors working in collaboration (2) 
have expressed the opinion that ‘ Although this hypothesis accounts for 
many of the facts in the Rosaceae, it meets with difficulty when applied to 
other families and is open to criticism on several counts ’. 
The criticisms of the views put forward by Eames, which the authors 
describe as ‘originating with Professor Jeffrey ’/are, in the words of their 
authors, as follows : ‘ In the first place, the transitional stages from a woody 
to an herbaceous condition, which it cites, and which form, indeed, the 
1 Contribution from the Laboratories of Plant Morphology of Harvard University. 
[Annals of Botany, Vol. XXXV. No. CXXXVIII. April, 1921.] 
Q a 
