208 



MORPHOLOGY 



Leaves. The leaf is very characteristic in form and venation (fig. 

 465), the broadly wedge-shaped outline, often more or less lobed, and 

 the forked veins resembling somewhat the leaves of maidenhair fern 

 and suggesting the common name. The mesophyll has the peculiar 

 character (transversely elongated and very loosely arranged cells) 

 described under Cordaitales and Cycadales (p. 193). 



467 



FiGS. 466, 467. Staminate strobilus of Ginkgo: 466, the clusters of strobili borne on' 

 dwarf branches; 467, a single strobilus, showing the character of the individual stamens 

 (a stalk ending in a knob and bearing two pendent sporangia). 



Strobili. The strobili are monosporangiate, and the two kinds of 

 strobili occur on different trees (dioecious). 



Staminate. The staminate strobili occur in loose catkin-like clusters 

 borne on the dwarf branches (fig. 466). The sporophyll (stamen) con- 

 sists of a stalk ending in a knob, from beneath one side of which two 

 (sometimes three to seven) pendent sporangia are borne (fig. 467). This 

 type of stamen suggests the epaulet type found among Cycadofilicales 

 (see p. 184). The development of the sporangium is regularly eusporan- 

 giate, as described under Cycadales (p. 194), 



