SPERMATOPHYTA 



6S 



America, Europe, India and the Arctic regions. Especially 

 fine representatives of the genus Cycadeoidea (Bennettites) 

 are found in the upper Mesozoic of Maryland, South Dakota, 

 Wyoming and Mexico. The genus Wielandiella from the Upper 

 Triassic (Rhaetic) had slender stems branching dichotomously 



Fig. 22. — The flower-bud of Cycadeoidea colossalis removed from between the 

 old leaf bases which form the heavy "armor" of the trunk of the plant. This is 

 such a flower-bud as that shown atf.b. in Fig. 19. i. Outer features of the cap- 

 sular disk of stamens which incloses the central cone ; bract-husk mostly cut 

 away ; diagrammatic. 2. Same as preceding but with a quarter of the bud cut 

 away so as to disclose inner seed cone and structure of the outer disk. 3. Dome 

 of bud drawn in rehef down to level of transverse section (T) and then continued 

 below by a median longitudinal section. The disk of stamens (D) divides into ten 

 fronds each of which sends up two prolongations to form the apical dome (T-C) 

 of twenty segments. The ten once decurved tips of the fronds envelop the seed 

 cone {A). At 5 are the synangia or complex pollen sacs. Compare with Fig. 21. 

 Natural size. (From Wieland.) 



and bore its flowers in the forks. Another genus, Williamsonia, 

 is also of varied structure and had a cosmopolitan distribution 

 in the Jura-Cretaceous. To the genera already mentioned 



