GINKGO ALES 



sr 



28, 29). There is great variability, however, both in size and 

 amount of lobing. 



The development of the foliage leaf has been described by 

 Fankhanser.*"' It is at first a protuberance embracing two fifths 

 of the circumference at the stem 

 apex. Soon a distinct emargina- 

 tion is developed which becomes 

 a deep incision. During devel- 

 opment the Ijlade is bent over at 

 the apex and the margins are 

 strongly inrolled. The leaves, 

 especially when young, are not 

 merely deeply two-lobed, but 

 each lobe is variously tootlied 

 or divided. 



In anatomical characters the 

 leaf resembles those of Cycads. 

 There is developed an evident 

 but not very thick cuticle. The 

 stomata are restricted to tlie 

 lower surface, the gimrd cells 

 being somewhat below the level 

 of the epidermis. A palisade 

 tissue is evident, Ijut somewhat irregular. A transfusion tissue, 

 such as was descriljed under the Cycads, appears also in the 

 , ._,, leaves of Gink- 



'^{k m'U0.y 90, cells of the 



TvW ''■*'^f- inner mesophyll 



/' elongating in a 



plane parallel 

 with the leaf 

 surface and de- 

 veloping numer- 

 ous and promi- 

 nent intercellu- 

 lar spaces. 



The leaves 

 are deciduous, a 

 rare haliit among Gymnosperms, being dis]ilayed in Conifers 

 only by Larix, Taxodium disticlmm, and Ghjptostvouui. 



'2.a,,— (.;;,ikn-> bihjijii, a cluster of 

 leitves and a mature seed. 



Fig. 2fi. — (_!inl;qn liloba^ a single leaf, slirnving venation. 



