162 MINNESOTA BOTANICAL STUDIES. 



ly SO in Liagora. Some forms can often be distin,c:iiishe(l only by 

 microscopic characters, while in other cases forms microscopically 

 very similar can be distinguished by differences in habit, branch- 

 ing, incrustation and the like. Botanists have differed greatly as to 

 the value of the various distinctions and only long work with the 

 living plants will probably settle the question. To make the mat- 

 ter worse, nearly all the older descriptions are entirely inadequate, 

 many of the illustrations which have been published are, to say the 

 least, insufficient and difficult to identify, and dried herbarium ma- 

 terial of these genera is very unsatisfactory for microscopic work. 



In the genus Galaxanra the monograph of Kjellman (Om 

 Floride-Slagtet Galaxaura dess Organografi och Systematik, F. R. 

 Kjellman, Stockholm, 1900) gives an admirable basis for taxonomic 

 work, and greatly simplifies the treatment of this genus. Agardlvs 

 corresponding work on Liagora (Agardh, J- G. De differentiis in 

 structura frondis, c^uae in diversis Liagorae speciebus observantur. 

 Analecta Algologica III.: 96, 1896), is not so satisfactory, largely 

 owing to the entire lack of illustrations. 



In view of these facts it has seemed best to describe fully, and 

 in most cases w'ith illustrations, all the forms which I have exam- 

 ined, with the exception of a few well known species of wide dis- 

 tribution, in the hopes that this treatment may lead to further study 

 of these interesting and too little known genera. It has appeared 

 necessary to describe a number of these forms as new and this has 

 seemed more desirable than an attempt to identify them with the 

 numerous species described in most cases from distant parts of 

 the world, and with such slight attention to detail as to be practical- 

 ly nomina nnda. 



Key to Sections of Liagora. 



I. Decalcified frond gelatinous; central cj^linder composed of large 

 primary cylindrical filaments and smaller filaments which surround these 

 and penetrate among them; cortical filaments of elongated cells con- 

 tracted at the nodes, ending in nuicli l>ranche(l heads of moniliform 

 cells; antheridia small. Eu-Liagora J. Ag. 



II. Decalcified frond soft mucilaginous; central cylinder composed 

 of large primary cells which are close packed and often angular and of 

 small cylindrical filaments, which surround the larger filaments and only 

 occasionally penetrate between them. 



1. Cortical filaments as in Eu-Liagora. 



Corymbosae sect. nov. 



