OF LOWER GREEN SAND PLANTS. 



39 



(Lignier, 1894, p. 50) are regularly arranged and closely packed. 

 lu the new sections of the type-specimen of B. Gibsonianus (see 

 p. 46) some portions of the inner tissues of the embryo are 

 beautifully preserved, and show also a small-celled epidermal 

 layer surrounding them. In an American species exceedingly 

 like B. Gibsonianus, Wieland has found a younger stage in the 

 seed-development which shows the internal cavity filled with a 

 pro-embryo (see Wieland, 1904 & 1906). 



Text-fig. 12. Bcnnett-ites Gibsonianus, Carr. The base of a tangentially 

 cut seed, cut so that it slopes through the basal vascular bundle, v. 

 st., the cells of the outer flesh, o., which run into the stalk ; s., the stone 

 layer ; i., the inner flesh of the testa. No. V. 8422. 



DISCUSSION OF THE LITERATURE. Adequately to discuss the 

 extensive and important literature which bears on B. Gibsoni- 

 anus would necessitate a lengthy treatment of the subject, much 

 of which is highly theoretical, and is therefore outside the scope 

 of the present volume. A few points which bear especially on 

 the Lower Greenland species may, however, be noted. 



