604 



BOTANY 



PART II 



Fossil Gymnosperms ( 15 ) 



In contrast to what was seen to be the case for the Pteridophyta, Gymnosperms 

 have not yet been detected in Cambrian and Silurian strata. They appear first in 





Mil 



^-" 





FIG. 598. 1, Cordaites subglomeratus, longitudinal section of a male flower -bud; b t investing 

 bracts ; a, stamens with several anthers. 2, A pollen grain ; the prothallial cell is separated 

 by a curved wall while the rest of the grain is divided into a number of cells. 3, C. Williamsoni, 

 longitudinal section of a female inflorescence; b, leaves; s, seed in longitudinal section. 

 4, C. Grand' Euryi, longitudinal section of an ovule, showing the deep pollen chamber in the 

 nucellus containing a number of pollen grains. (After RENAULT.) 



the Devonian, but are sparingly represented and first form an important constituent 

 of the flora in the Carboniferous. From the Cycadofilices, which possessed steins 

 with secondary thickening and fern-like foliage and had been regarded as Pteri- 

 dophyta, OLIVER and SCOTT have recently separated the Pteridospermeae ; which 

 may be shortly characterised as fern - like seed - plants. These have been con- 

 sidered in connection with the Pteridophyta (p. 534). 



Cordaitaceae. Cordaites is a peculiar type confined to the Palaeozoic rocks. 

 Owing to the excellence of the preservation of the remains, its morphology is as 



