VASCULAR ANATOMY OF THE MEGASPOROPHYLLS 

 OF CONIFERS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 208 



Hannah C. Aase 



(WITH 196 FIGURES) 



Introductory and historical 



The megasporophyll in Coniferales has been the subject of 

 much investigation and discussion, as on the interpretation of this 

 structure depends to a great extent the views held in regard to 

 the relation of living conifers to fossil forms, and the interrela- 

 tion of living genera. If the scale in Pinus, the ligule in Araucaria, 

 and the epimatium in Podocarpus represent a dorsal outgrowth 

 of the bract, there is added a strong argument in support of the 

 contention that the conifers have sprung from lycopod stock. 

 If the megasporophyll represents a metamorphosed fertile shoot 

 and its subtending bract, there exists a suggestive likeness to the 

 Cordaitales, in which the presence of bracts on the shoot makes 

 its identification as a shoot less difficult. Again, if the scale in the 

 Abietineae represents an axillary shoot and the ligule in Araucaria 

 represents a dorsal outgrowth, two other possibilities may be sug- 

 gested: either the Coniferales have a double origin, or the Cor- 

 daitales included not only forms with compound strobili in which 

 the scale is a metamorphosed structure, but also forms with simple 

 strobili in which the scale is a ligular outgrowth of the bract. All 

 these four views are supported by various investigators. Cor- 

 relative with the views taken as to the origin of the group as a 

 whole are the views as to the interrelation of genera ; forms which 

 may be considered as progenitors according to one theory may be 

 the descendants according to another, or there may exist no 

 relation. 



The investigators before 1868 were concerned chiefly with 

 gross observations of development and abnormalities. Rather 

 277] [Botanical Gazette, vol. 60 



