THE GREEN ALGAE OF NORTH AMERICA 409 



CAULERPA Lamouroux, 18093, p. 30. 



Frond composed of a creeping stolon (wanting in one species), 

 giving out rhizoids below and branches above. The latter of 

 various form, usually erect, but sometimes prostrate ; simple or 

 branched. Marine. 



A remarkable genus, of many species of very diverse shape 

 and degree of vegetative differentiation, but all constructed on 

 the type of a creeping rhizome-like stem, giving out filamentous 

 rhizoids below, and erect branches above. For the latter the 

 word " frond " will be used in the following pages, in a special 

 limited sense. These fronds vary from the simplest filaments to 

 very elaborate branching structures, often simulating to a sur- 

 prising degree the forms of higher plants, so that most of the 

 sections of the genus are named for these resemblances, and 

 these names often give as good an idea of the habit as can be 

 obtained from technical descriptions. The entire plant, how- 

 ever differentiated, is continuous throughout, not divided into 

 cells, and the only propagation known is by the breaking off 

 from the frond of some part, which continues to grow as a dis- 

 tinct individual. Pieces of either rhizome or frond can de- 

 velop in this way, so that, in one sense, all the plants on a 

 whole stretch of coast may be a single individual, broken up by 

 various causes. 



While very various types of form are found in various species, 

 the lines cannot be sharply drawn, one form passing insensibly 

 into another. Being tropical or subtropical plants, much the 

 greater part of the species have been founded on dried speci- 

 mens only, often very fragmentary and insufficient specimens, 

 obtained by collectors by no means specialists in algae. Thus 

 it has frequently happened that species have been founded on 

 specimens showing markedly different characters, while later 

 investigation has brought to light plants with fronds of both 

 types growing from the same stem. 



The careful revision of the genus by Mme. Weber van Bosse, 

 1898, founded largely on the study of living plants and by com- 

 parison of practically all the original specimens, has been fol- 

 lowed in the following descriptions. Many varieties and forms 

 are given in her work, corresponding largely to former species, 



