The Genus Riccardia in Chile. 133 



median portion are longer and narrower than the wing-cells, 

 measuring about 60 x 30/*. The ultimate or tertiary branches 

 measure 0.15-0.2 mm. in width, the secondary branches 0.2-0.3 

 mm., and the primary branches 0.3-0.45 mm. The wings, which 

 form so marked a feature of the ultimate branches, are narrower 

 and less distinct on the secondary branches and still narrower on 

 the primary branches, tending to disappear altogether before the 

 main axis is reached. 



Photosynthetic branch-systems of the complexity just described 

 are not always developed and are to be expected only at some little 

 distance from the apex of the main axis. As this apex is 

 approached the systems become simpler and simpler, merely 

 because they are younger and have not yet had time to develop. 

 The branches in the vicinity of the apex, in fact, are so simple that 

 they give no indication of the intricate systems into which they will 

 presumably develop. Sometimes, if conditions are unfavorable, 

 the branch-systems remain relatively undeveloped and give rise to 

 plants which seem very different from typical specimens. It was 

 apparently upon plants of this sort that Aneura umbrosa was based, 

 and the writer agrees with Stephani (27, p. 684) in regarding this 

 species as a juvenile form of Riccardia crispa. According to 

 Schiffner Aneura umbrosa is characterized by a thallus-margin 

 which is neither pellucid nor composed of a single layer of cells. 

 This description certainly applies to the axis and to most of the 

 branches of the fragmentary type specimen, but would apply just 

 as well to the apical portion of the thallus in typical R. crispa. A 

 few of the ultimate branches in A. umbrosa, moreover, show a 

 unistratose wing three cells wide and a thickened median region, 

 thus justifying still further the reduction of the species to 

 synonymy. 



In his study oi R. crispa the writer has seen neither stolons nor 

 rhizoids, and the earlier descriptions make no mention of such 

 structures. According to Stephani the main axis is simple or 

 repeatedly forked in the upper part and Schiffner's figure shows 

 an axis with a single fork. Although no forking axes have been 

 observed in the present study, this is doubtless due to the small 

 amount of available material. It may be noted that Schiffner's 

 figure shows a thallus in which the photosynthetic systems are 

 rather sparingly branched, and the type material of the species is 



