428 University of California Puhlications in Botany [Vol.7 



become polystromatic. The eosta is very conspicuous and of the same 

 anatomical structure in both, it emits opposite, nearly straight to irreg- 

 ularly bent, distinct nerves. Tlie ramification from the lamina is 

 marginal, solitary segments growing out to form new blades. When 

 the lamina has worn away numerous shortly stipitate proliferations 

 grow out from the edges of the old, flattened costa. The hapter is a 

 small disc. 



The cystoearps are scattered between the nerves, and the same 

 position is occupied by the spermatangia and tetrasporic sori, the 

 latter often occupying the entire space between the costa and the 

 margin of the frond, only leaving the nerves free. Further, both 

 species have exactly the same mode of apical growth (see below). 



The Calif ornian plant differs from the true D. quercifoUa in the 

 following characters : The frond is more oblong, Ungulate, and, except 

 for the segments growing out to form branches, entire, or only slightly 

 undulate and denticulate. The frond of D. quercifoUa Bory is more 

 broadly obovate in outline, more or less deeply sinuate-dentate, young 

 intact specimens recalling the leaves of the common European Quercus 

 rohur and very similar to D. sinioosa of the northern coasts. The 

 anatomical structure is the same in all these species. To judge from 

 the material examined there is some little difference in the costa 

 between the Californian species and D. quercifoUa. In the former 

 (fig. 1) the central lamella consists of one layer of very large cells, 

 corresponding to the monostromatic lamina; and even the innermost 

 cortical cells are much smaller, each cell, on the cross-section, sup- 

 porting one or two rows of radially arranged cells. In D. quercifoUa 

 there generally are as much as five layers of large cells, because the 

 inner cortical strata are more similar to the central lamella and con- 

 trasting with the outer radial rows of small cells, but in other cases 

 this structure has proved to be submitted to some variation, so we 

 should not lay very great weight upon this difference. 



Anyhow we have to do with two distinct species belonging to the 

 same genus. D. quercifoUa Bory is sometimes called Schizoneura 

 quercifoUa (Bory) J. Ag. and, if we follow Agardh, it lies near at 

 hand to describe the other as a new species of Schizoneura. But if 

 we advance deeper into this matter we shall find that Agardh 's genus 

 is a mixtum compositum, and that we cannot arrive at a solution unless 

 entering upon the history of the genus Delesseria and the systematic 

 value of some of the genera created by Agardh in Sp. Alg. Ill :3 

 (1898). 



