1905.] PRINCIPLE OF SYSTEMATIZING CORAJJJNJE. 119 



aspergillum must certainly be worthy enough to restore the genus Lithothrix. 

 Eecently an elaborate work appeared under the title " Corallinaceaa of the 

 Siboga Expedition." In part II of that work Madam A. Weber van 

 Bosse subjects to revise the large part of the Coralline, basing it on a 

 minute study of the structure of articuli and genicula. It resulted in many 

 amendments in the definitions of several genera ; and in the introduction 

 of the new genera Metagoniolitlton (for AmpJriroa stelligera and its allies) 

 and Litharthron (for Amphiroa australis), and in re-establishing Lithothrix 

 for Amphiroa aspergillum. A new synoptical key to all genera of the 

 Corallinas is given in the work. The characters primarily utilized in her 

 key for distinguishing the genera lie in the structure of the articuli and 

 genicula, and the position of the conceptacles and the form of articuli seem 

 to have been regarded as next importance. 



Before Weber's work we have two more keys to guide to separate the 

 three genera Corallina L. Amphiroa Lamx. and Cheilosporum Zanard. 

 The one is by Schmitz and Hauptfleisch in Engler and Prantl's "Pflanzen- 

 familien," 1 ' and the other is by Heydrich. 2 ' These two keys are applicable 

 to certain special and limited forms only. 



As I 3 ' have said in a former paper, " a group may be more sharply 

 defined by the peculiarity, if any, of genicula, rather than by mere external 

 forms of articuli." It is a matter of question, however, if for systematic 

 purpose the vegative character can with propriety be made to supersede 

 the reproductive character in importance. From this stand point of view I 

 can not wholly agree in the principle of arrangement done by Madam 

 Weber van Kosse. Still it can not be denied that her work opened a way 

 towards smoothing awav the confusion that had existed in the system of 

 the Coralline. 



All attempts to establish a system of Corallinre merely by the position 

 of the conceptacles are confronted by various difficulties. Equally difficult 

 it would be to base a system solely upon the external shape of the articuli. 

 The position of the conceptacles in a genus is often as variable as the 

 shape of articuli. 



To what degree the fronds of the Corallinaceous algae are variable or 

 which of their characters are constant, is a matter difficult to determine 

 unless the plants are closely observed at different seasons and under different 



1) I Theil. 2 Abt. p. ,540. 



2) Ueber die Coral. (Ber. d. Deut. Bot. Gesel. Bd. XV. p. 40.) 



3) Study of Genicula. p. 41. 



