b 



308 MORPHOLOGY OF ANGIOSPERMS 



dell, 8 however, lias found that the bundles of the cotyledons 

 show fairly well-developed cryptogamic wood. Fig. Ill, W, 

 taken from Worsdell, makes the truth of this statement appar- 

 ent. The anatomical evidence leads to the conclusion that we 

 have in Ginkgo a comparatively modern genus as compared with 

 the living representatives of the cycadean stock. Distinct foliar 

 gaps are present, which, taken together with the large leaves 

 and the rnulticiliate sperms, point strongly to a fllicinean an- 

 cestry. 



COXIFERALES 



The Coniferales are the prevailing Gymnosperms of the 

 present day, and it is not surprising that they should present 

 few anatomical features which can he considered ancestral. 

 Their usually small acicular leaves offer a striking contrast 

 to the large fern-like foliar organs of the older gymnospermous 

 groups. On account of the peculiar appearance of their foliage 

 it is not to be wondered at that they should have been associated 

 by Renault, 2 Campbell, 5 and Potonie n with lyeopodineous an- 

 cestors. Recent work on the anatomy (Jeffrey 111 ) of vascular 

 plants in general appears to show that in the case of the Conife- 

 rales the microphyllous habit has merely an ecological interest; 

 for, unlike all the Lycopodiales, they have well-marked foliar 

 gaps in their cauline woody cylinder. 



The researches of Worsdell s on the foliar bundles of the 

 Conifers have resulted in a clear demonstration of striking 

 pteridophytic features. Fig. 112, X, represents a cross-section 

 of the cotyledonary bundle of Cephalotaxus drupacea. On the 

 lower side of the iibrovascular strand centrifugal wood, such 

 as is ordinarily present in the bundles of the Conifers, can lie 

 made out. On the upper side of the bundle are large, thick- 

 walled elements, which are to be compared with tire centripetal 

 tracheids of the cycadean bundle in Fig. Ill, U. Fi;r. 11-. Y, 

 shows a longitudinal section of a cotyledonary bundle of C. 

 Fortunei. On the left are some pitted tracheids of the second- 

 ary wood. In the center of the bundle is the disorganized pro- 

 toxylem, while on the right is a single reticulated tracheid of 

 the ancestral centripetal wood. The cotyledonary bundles of 

 Cephalotaxus are consequently mesarch like those of the ordi- 

 nary leaves in Cycads, but show striking signs of degeneracy 



