VOLUME LXIII 



NUMBER 6 



THE 



Botanical Gazette 



JUNE iqij 



development of dumontia FILIFORMIS 1 



II. DEVELOPMENT OF SEXUAL PLANTS AND GENERAL 



DISCUSSION OF RESULTS* 



Grace A. Dunn 



(with plates xix-xxii and seven figures) 



Introduction 



y Dumontia filiformis (Huds.) Grev. is a red seaweed which is 



widely scattered in the temperate zones. It has been reported 





as occurring on the Auckland and Falkland Islands (2), on the 

 shores of Alaska, and is very common in northern Europe. This 

 species was first found on the Atlantic coast of North America, by 

 the writer, at South Harpswell, Maine, in June 1913. Tetrasporic 

 i and cystocarpic plants were collected at that time. Sterile plants 



were collected by Thaxter at Kittery Point, Maine, in April 1914 3 

 These are the only two points on this coast where plants of 

 Dumontia have been reported to occur. 



In all probability Dumontia has become established on the coast 

 at South Harpswell some time between 1909-1913. F. S. Collins 

 collected at South Harpswell in the early part of July for 6 years 

 (1902-1905 and 1908-1909) in the same pools in which Dumontia 

 was abundant in July 1913 and 1914. He states that he has never 

 found a single specimen of Dumontia in any of these pools, and if 



1 Botanical contribution from the Johns Hopkins University, no. 55. 



2 First paper entitled "The development of the tetraspores." Plant World, 

 I 19: 271-281. figs. 2. 1916. 



3 Personal letter from F. S. Collins. 



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