GINKGOALES 



197 



bearing several ovules and terminating in a scaly bud (fig. 225). In 

 1900 Seward and Gowan (28) reviewed the whole situation, studied 

 additional abnormalities, and coincided with the conclusions of Fujii. 

 And now Shaw (50), investigating the vascular anatomy of the 

 strobilus, dissents from the current view that the collar is a much 

 reduced megasporophyll. It seems that the bundles of the collar 

 show inverse orientation, and a 

 corapsLxisonrnth. Lagenostoma sug- 

 gests that the collar of Ginkgo is 

 a vestige of the cupule that in- 

 vested seeds of the Lagenostoma 

 type. This claim for the cupule 

 nature of the collar is most in- 

 teresting, and if it is the true one, 

 it even more strongly emphasizes 

 the close connection of Gink- 

 goales and Cycadofilicales. 



The evidence at present sug- 

 gests that the structure under 

 discussion is a strobilus bearing 

 two or more megasporophylls, 

 which are usually reduced to the 

 so-called "collars," but which 

 sometimes resume their original 

 leaflike character. These ab- 

 normal ovuliferous leaves are 

 most suggestive of the ovulif- 

 erous leaves of the Cycadofilicales, and hence of the origin of the 

 ovulate strobilus of Ginkgo. While the stalk of the strobilus re- 

 sembles the petiole of a leaf, it is quite different in its structure. 

 A transverse section of a petiole shows the two bundles already 

 mentioned as representing the double leaf trace; while a trans- 

 verse section of the stalk of a strobilus shows the four bundles 

 which would be expected in a stem bearing two leaves (collars) at 

 its apex (figs. 226, 227). When more than two ovules are borne on 

 one stalk, there are twice as many bundles in the stalk as there are 

 ovules at its apex, just as there should be if each collar were a mega- 



FlG. 224. — Ginkgo biloba: axis bearing 

 seven ovules, each with a pedicel. — After 

 Sprecher (47). 



