The Genus Riccardia in Chile. 103 



tative axes with the exception of the rhizoids and shme papillae. 

 Their complexity in outward form is brought about by the 

 development of more than one kind of axis, the branches being 

 clearly differentiated from the main axis and showing a further 

 differentiation when compared with one another. The Javan 

 R. Jiymeiiopliylloides Schiffn. (20, p. 54) may be taken as an 

 example. In this remarkable plant, as described and figured so 

 clearly by Goebel (11, p. 280, /. ly/, lyS) the thallus shows a 

 subterete axis with rounded edges, unlimited growth, and no 

 indication of wings. The primary branches, however, which 

 arise in subopposite pairs at fairly regular intervals along the 

 main axis, are soon limited in their growth and show a broad 

 median region three or four cells thick, sharply set off from 

 ecjually broad unistratose wings. These primary branches bear 

 closely crowded secondary branches, likewise limited in growth, 

 in Avhich a further differentiation in the same direction mani- 

 fests itself, the median portion l^eing reduced in width and the 

 wings increased. The primary and secondary branches form 

 branch-systems to which the function of photosynthesis is largely 

 restricted. The axis on the contrary, as emphasized by Goebel, 

 is largely mechanical in its function but also plays a part in certain 

 processes connected with nutrition, such as the storage and 

 transportation of foods. 



In R. hymenophylloldcs the axis is prostrate and partakes to 

 a certain extent of the nature of a creeping caudex or rhizome. 

 But in Aneiira fucoides, where the axis is erect in older plants, 

 the same type of differentiation is present, and the basal part of 

 the axis often gives off another type of branch in the form of 

 stolons, the function of which is to affix the plant to the sub- 

 stratum. The stolons resemble the axis in being subterete and 

 wingless, but their branching is sparse and irregular, the branches 

 representing new stolons. Goebel has likewise figured the thallus 

 of A. fucoides (11, /. ij2, 155) and emphasizes the fact that the 

 stolons are not organs siii generis. They are merely modifications 

 of photosynthetic branches, and a direct change from such a branch 

 into a stolon can sometimes be observed. 



The histological differentiation in such complicated types is 

 perhaps most strongly marked in the main axis. As an expression 

 of their mechanical function there is present a distinct sclerotic 



