ALTEKI^ATIOX AXD PARTHEXOGENESIS 11^ PADIXA* 



By James J. Wolfe 



The species with which these experiments were carried on is very 

 abundant at Beaufort, and is reported as common on the coasts of 

 Florida and the West Indies. Algologists have very generally re- 

 ferred it to Paclina durvUlaei Bory, but early in the course of this 

 work the writer became convinced that this reference was • incorrect. 

 Specimens were then submitted to Dr. Farlow of the Harvard Cryp- 

 togamic Laboratory for his opinion in the matter. After his usual 

 thorough examination, the details of which are reserved for a later 

 paper dealing with the general morphology of the species, Dr. Farlow 

 writes that he regards the form as P. variegata (Kg.) Vickers (8 & 9). 

 Furthermore, Dr. W. D. Hoyt states that Mr. F. S. Collins, who has 

 worked on his collection of Beaufort algae likewise refers this form 

 to P. variegata. It is therefore reasonably safe to conclude that the 

 common species of our eastern shores and the one upon which these 

 experiments are based is P. variegata (Kg.) Vickers. 



This plant presents the interesting condition seen in Dictyota and 

 many red algae of three individuals in one life cycle — male, female, 

 and tetrasporic. On casual inspection the three are quite similar, 

 but under the microscope, even though their vegetative cells are alike, 

 they can be readily distinguished by their reproductive structures, at 

 least in the great majority of cases. With practice one acquires con- 

 siderable skill in distingiiishing them with the hand lens and even 

 with the unaided eye. 



In 1904 Williams (7), working with I)icti/ota diclwtoma. pre- 

 sented very fully and completely the cytological evidence for the 

 alternation of the asexual or sporophytic generation with the sexual 

 or gametophytic. Hoyt in 1910 (1) published a brief account of his 

 cultures from fertilized eggs and tetraspores of D. diclioioma, show- 

 ing, as was expected from the cytological evidence previously brought 

 out, that without exception the fertilized eggs produce tetrasporic 



*Contribution from the Laboratory of the Bureau of Fisheries, Beaufort. N. C. This paper, 

 in somewhat shortened form, was read before a joint session of the Botanical Society of Amer- 

 ica and the Botanical Section of the A. A. A. S. at their 1918 meeting in Pittsburg. 



78 



