THE MARINE AL&J2 OF THE BUTCH WEST INDIES 70 



original basal rhizoid was present and was vigorously developed, 

 forming the sole and efficient means of attachment to the rocks in 

 rough water. Such plants are difficult to distinguish from Chceto- 

 morpha, but the author points out a number of minor characteristics 

 which serve to separate these two genera. 



The curious structures detected on Liagora by Dr. Howe and 

 described by him (1920) as " Monosporangial discs " are discussed in 

 the appendix. They occur on several species collected by Dr. Borgesen, 

 but most abundantly on L. elongata. They are described and figured 

 in various stages of development, including a fruiting plant bearing a 

 two-celled sporangium, whereas Dr. Howe had only found monospo- 

 rangia, these being fairly frequent. Dr. Borgesen failed to detect any 

 organic continuity between the discs and the Liagora host-plant, and 

 therefore inclines to Dr. Howe's alternative view that the discs are 

 independent structures living in the mucous layer of Liagora. 



These instances serve to indicate the great value of Dr. Borg-esen's 

 work and the thoroughness with which he has carried out his researches. 

 His monograph will be of the utmost service to all concerned in the 

 investigation of the algal flora of tropical America — and its value is 

 immeasurably enhanced by the wealth of beautiful drawings, which 

 reveal at a glance the structure of the plants and make clear all the 

 points at issue. Moreover, the discovery of so high a proportion of 

 novelties — five genera, sixty species, and numerous varieties and forms 

 amounting to nearly one-fifth of the total list — gives the work such 

 an importance as to render it indispensable. 



In a final note on the geographical position of the algal flora of 

 the Danish West Indies the author calls attention to its striking 

 resemblance with that of the Indo-Pacific Ocean. This is especially 

 applicable, he tells us, to certain, undoubtedly veiy old, groups of 

 Chlorophycea?. The Rhodophyceos, on the other hand, show less 

 resemblance to those of the Indo-Pacific, but are more closely related 

 to those of the Mediterranean-Atlantic. The great similarity between 

 the algae of the West Indies and those of the Indo-Pacific — regions 

 which are now so completely separated — is explained by the existence 

 of an ancient connexion between the two oceans. 



A. AND E. S. Gepp. 



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