250 MORPHOLOGY OF GYMNOSPERMS 



The ovuliferous scale of Pinaceae, therefore, has been regarded 

 successively an open carpel, a placenta, a flattened axillary shoot, 

 the first two leaves of an axillary shoot, the first and only leaf of an 

 axillary shoot, a ligule, fused outer integuments, and a chalazal out- 

 growth. To select among these views is more difficult than impor- 

 tant. The testimony would seem to favor Bradn's general view, 

 and this would relate the megasporangia properly to the abaxial 

 surface of their sporophylls, the relation held by the microsporangia. 

 Moreover, it was evidently the situation in the ovulate strobilus of 

 some of the Cordaitales at least, and the historical connection of Pina- 

 ceae and Cordaitales is fairly clear. Amid all the possible details 

 of views, the really important fact is reasonably substantiated that the 

 scale and its ovules, in Abietineae at least, in some way represent a 

 modified axillary shoot, corresponding to the characteristic dwarf 

 shoot of the group; and therefore, that the strobilus is a compound 

 one, as among the Cordaitales and Gnetales. 



Among Taxodineae and Cupressineae bract and scale form a 

 single structure; but the two distinct and dorso- ventral apices, and 

 the two sets of vascular strands with opposing orientation (the xylem 

 of the one facing the xylem of the other) , make the inference reasonable 

 that the same structures are represented as occur among the Abietineae. 



Investigators claim that the case of the Araucarineae is very 

 different (figs. 272, 273). In Araucaria a superficial examination 

 seems to show a fused bract and ovuliferous scale, as in the Cupres- 

 sineae, but some insist that there is no such evidence of its double 

 nature. Even if the ligule of Araucaria be interpreted as an 

 ovuliferous scale, it is doubtful whether a ligule is present in 

 Agathis. Since there seems to be no convincing evidence, many 

 would prefer to regard the bracts of Araucarineae as simple sporo- 

 phylls (117), some of which are ligulate. Thompson (164) believes 

 that vascular anatomy proves that the araucarian ovulate strobilus 

 consists of simple sporophylls, while Aase (233) is inclined to believe 

 that the sporophylls are compound. In the vascular supply bimdle 

 for sporangia (including microsporangia) there is developed an 

 inverse orientation. Among the other tribes of Pinaceae there are 

 two such orientations, indicating a different condition; while in 

 the megasporophylls of podocarps there is the single inverse orien- 



