174 THE EVOLUTION OF CONTINUITY 



the hydrozoal sporosac-gonoblastidium, and it is our belief 

 that the Calamites were also of Continuously Zooidal 

 derivation. 



And this suggested derivation of Gymnosperms is sup- 

 ported by the case of the Angiosperms. 



There would seem to be clear geological evidence that 

 the Angiosperms appeared on this globe suddenly. Gymno- 

 sperms have flourished since Palaeozoic times, as their fossils 

 plainly show, but the first evidence of Angiosperms is in 

 the Cretaceous strata of Mesozoic times, where their fossils 

 are met with in great variety. 



But, as has been already said, it is most improbable 



OVult 



A i 



Fig. 49. — Suggested derivation of the Gymnosperm cone from 

 the Hydrozoal sporosac-gonoblastidium. A, hydrozoal sporo- 

 sac, containing sexual elements. B, ovule, carpel, and scale 

 of female pine-cone, c, stamen and pollen-sac of male 

 pine-cone, d, female gonoblastidium with successions of 

 sporosacs. e, female pine-cone with successions of ovules, 

 carpels and scales ; diagrammatic, f, longitudinal section of 

 part of cone of a Calami to. (Fig. f, after Scott.) 



that the Angiosperms have been derived from Cycadophytes, 

 Gymnosperms, or any preceding terrestrial plant-types ; the 

 truth would seem to be that they were a fresh stock derived 

 from the sea or lakes which ages before had supplied the 

 Gymnosperms. However, during the ages which passed 

 from the appearance of the Gymnosperms to that of the 

 Angiosperms, the Hydrozoal type which supplied the former 

 plants had been itself evolving ; and doing so in one special 

 direction. It had now come to be represented in part by 

 a type in which the reproductive structure was much more 



