GINKGOACE^. 247 



Class GINKGOALES. 



Family GINKGOACE^. 



The genus Ginkgo (or Salishuria), the Maidenhair-tree of China 

 and Japan, has long been recognized as an isolated member of the 

 Coniferse ; but in recent years it has been shown that there are 

 good grounds for giving expression to its peculiarities by instituting 

 a special division of Gymnosperms for the inclusion of this mono- 

 typic genus. 



In a recent number of Bie NatiirUehen Pflan%enfamUien by 

 Engler & Prantl, the name Ginkoales is adopted as a class- 

 designation, and in this subdivision of the Gymnosperms is included 

 the family Ginkgoacese, represented by the single living genus 

 Ginkgo. The following definition of the Ginkgoacese is quoted 

 from Engler & Prantl : — ' 



"Flowers unisexual, dioecious, without perianth. Male flowers 

 shortly stalked, long, and of loose or open structure. Stamens 

 with two free pollen - sacs. Pollen spherical, producing two 

 spermatozoids before fertilization. Female flowers supported on 

 a long axis bearing usually two terminal carpels, and rarely more 

 than two ; these are stalked spherical bodies, the seed being 

 surrounded at the base by an enveloping collar -Uke structure. 

 Ovules with one integument. The ripe seeds have a fleshy outer 

 coat and a hard, strong, inner coat. Embryo with two cotyledons. 

 Leaves stalked; the lamina divided into two or more lobes." 



The most important advance made in recent years as regards our 

 knowledge of the morphology and natural position of Ginkgo is the 

 discovery by the Japanese botanist Hirase ' of large cUiated and 

 spirally coUed spermatozoids, which are produced in the pollen-tube 

 shortly before fertilization. Among Conifers the male generative 



1 Engler & Prantl (97), p. 19. 

 •■' Hirase (97) (98). 



