42 Oliver and Salisbury. — On the Structure and 
the ribs passed out into free tentacles at the apex, each with its own vascular 
bundle, and in the young seed the conjunctive tissue between the ribs was 
Text-fig. 13. Transverse sections (diagrammatic) passing through the apex and the lageno- 
stome of Physostoma (a), Conostoma oblongum (b), and Conostoma anglo-germanicum (C). 
Parenchyma shaded : testa in black : ‘ blow-off ’ white. 
much less developed than in mature specimens, perhaps an ontogenetic 
recapitulation of phylogeny . 1 This is still further borne out by the gradual 
1 Oliver : Ann. of Bot., vol. xxiii, p. too, PI. VII, Fig. 29. 
