igig] DVPLER— TAXUS 361 



in some cases the smaller xylem elements are on the outside of the 

 bundle, indicating a possibility of exarch structure (fig. 42). In 

 addition, the xylem elements, in the terminal portions of the 

 bundles, become more and more placed toward the center of the 

 bundle, giving virtually a concentric bundle of a few xylem cells 

 surrounded by the phloem portion of the bundle (fig. 41). No 

 transfusion tissue was found elsewhere than in the scales. 



Discussion 



Perhaps the two most important features of the staminate 

 strobilus of Taxus are the peltate sporophylls and the character of 

 the vascular bundles of the scale and sporophylls. The peltate 

 (epaulet) type of stamen occurred among the Paleozoic Cycado- 

 filicales, in the Crossotheca forms, but the sporangia were bilocular 

 and dehisced by a longitudinal slit along the adaxial face, the 

 bilocular character being different from that of the modern gym- 

 nosperms. Peltate stamens are not known in Bennettitales, and 

 none occur in the Cycadales. The peltate stamen has been carried 

 forward to modern plants through the Cordaitalean line, in all 

 probability, although so far as is known the stamens in the Cordai- 

 tales bore terminal erect sporangia. As Coulter and Cham- 

 berlain state, however, "it cannot be supposed that the stamens 

 of so great a group were uniform in type," and it is very possible 

 that peltate stamens occurred there also. The sporophyll of 

 Ginkgo gives a suggestion of the peltate type of stamen, in occasion- 

 ally having more than 2 sporangia, in the regular occurrence of more 

 than 2 sporangia in fossil forms, and in the possibility, pointed out 

 by Miss Starr, that the mucilage cavity replaces abortive spo- 

 rangia. Among Coniferales there is a suggestion of the peltate 

 stamen in the Araucarineae, and stamens of true peltate form occur 

 in such forms as Widdringtonia, Torreya, and Taxus. In Torreya 

 the true peltate character is generally obscured in the adult sporo- 

 phyll owing to the development of the resin cavity from 3 of the 7 

 sporangium beginnings. Hence it is seen that peltate stamens, in 

 one form or another, are scattered from Cycadofilicales to modern 

 conifers, and there is no necessity of regarding such a sporophyll 

 as that of Taxus as being of recent evolution. Assuming peltate 



