
SPERMATOPHYTA 419 
conifers. It is generally believed that both it and the conifers 
are descended from an extinct order of gymnosperms, the Cor- 
daitales, which was a dominant element of the flora of the 
Paleozoic Age. This relationship 
explains the similarities between 
Ginkgo and the conifers. The Cor- 
daitales appear to have been derived 
either from the Cycadofilicales or 



eae 
Tones 
GEAR 
GR 
DS 
ans 
Cy cadales 
Coniferales 




Modern Ferns 
Ginkgoales 
Fic.473. Branch of Ginkgo bearing 
strobili of male sporophylls. (x 2) 
from their ancestors, so that 
Ginkgo is related through 
the Cycadofilicales to the 
Cycadales. While the cycads 
and Ginkgo have some primi- 
tive features in common, the 
cycads have retained primi- 
tive characters to a greater 
extent than has Ginkgo. A 
diagrammatic representation 
of the relationship of Ginkgo 
is clearly shown in Fig. 474. 
Ginkgo is almost unknown 
in the wild state, and the 
order Ginkgoales was on the 
road to extinction when Ginkgo began to be cultivated. In 
former ages the order included a number of genera and had 
a wide distribution. 
Cycadofilicales 

Fig. 474. Diagram showing relation- 
ship of gymnosperms 
