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 Braun'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 those who have investigated the structure say that there is 

 no such evidence of its double nature. Even if the ligule of Araucaria 

 be accepted as a vestige of the ovuliferous scale, there is no ligule in 

 Agathis. It seems to be a needless forcing of the situation to regard 

 the o\ailiferous bracts of Araucarineae other than they seem, that is, 

 simple sporophylls (117), some of which are ligulate. In a recent 

 study of the vascular anatomy of the ovuliferous structure of conifers, 

 Thomson (164) has found definite evidence that the araucarian ovu- 

 late strobilus consists of simple megasporophylls. In the vascular 

 supply bundle 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- 



