GINKGOALES 



197 



microsporangium (fig. 213). Coulter and Land's^ had found that 

 in Torreya resin ducts are formed from three of an original seven 

 sporangia, so that the sporophyll is really peltate, like that of Taxus. 

 In Ginkgo the mucilage cavity in the hump shows the type of de- 



FiG. 211. — Ginkgo hiloha: long shoot 

 with spur shoots bearing male strobili 

 and young leaves; about natural size. 

 — After Coulter. '55 



Fig. 212. — Ginkgo biloba: single 

 male strobilus, showing sporophylls, 

 each bearing two sporangia; X3.5. 

 — After Coulter. 'S3 



velopment which they found in Torreya. Since Baiera has regularly 

 more than two sporangia on a sporophyll, and Ginkgo occasionally 

 has more than two, the mucilage cavity might represent lost spo- 

 rangia. Against this theory, it can be urged that Baiera, with all its 

 sporangia, still has a hump, and that Ginkgo, in the rare cases with 

 more than two sporangia, has the hump just as well developed as 

 when there are only two. Further, the mucilage cavities in the leaf, 

 in early stages, look like those in the hump. 



