158 SETCHELL— PARASITISM AMONG RED ALG^. 



penetration, extreme dwarfing or condensation of the thallus may be 

 taken to indicate true parasitism of greater or less degree. At the 

 same time the reproductive organs present little if any metamor- 

 phosis. 



In color, parasites vary from little if any loss of pigment to cases 

 where none is present. Loss of color is always associated with 

 extreme penetration and very considerable dwarfing or condensation. 



It is only within the last thirty years that the fact has been 

 realized that there exists a group of peculiar and undoubted para- 

 sites among the red algse, although a few cases were noted before 

 that time. Probably the first reference to such a parasite is that by 

 Lyngbye in noting that certain tubercles on " Sphcerococcus Brodicci" 

 (Phyllophora Brodicci) called by him " Chcctophora memhranifolii" 

 and which had been considered to be the nemathecia of the plant 

 on which they were found, were no part of the '' Sphccrococcus" 

 but belonged to a parasite. This was in 1819 (p. 11, pi. 3, f. B, 3, 4). 

 In 1834 Lyngbye describes this plant in more detail, naming it 

 Chcetophora subcutanea (1834, pi. 2135), but saying nothing defi- 

 nitely as to its being parasitic. Kuetzing, in 1843 (P- ^77> pl- 45> 

 f. IV), re-described and named it Actinococciis roseus, seemingly 

 unaware of the earlier description of Lyngbye. The species, which 

 now bears the name A ctino coccus sub cutaneus (Lyngb.) Rosenvinge, 

 later became the object of a considerable discussion and difference 

 of opinion as to its exact nature (cf. Schmitz, 1893, etc.). It is 

 now recognized as a true parasite by most phycologists. 



The second parasite belonging to the red algse to be recognized 

 was Ricardia Montagnei described by Derbes and Sober in 1856 (p. 

 209, pl. i). This plant, usually assigned to the Bonnemaisoniacese, 

 forms ovoid red bladders of larger or smaller size, on the tips of 

 species of Laurencia. Its basal portion occupies the apical pit of 

 the branches of the Laurencia and penetrates into its tissue (cf. Olt- 

 manns, 1905, p. 326, f. 580). 



In 1874-75, Reinsch published his " Contributiones ad Algolo- 

 giam and Fungologiam " and in this he described a number of tu- 

 bercles found on various red algse which be believed to be parasitic 

 members of the same group. Among the tubercles thus described 

 by Reinsch, some are undoubtedly simply warts or pathologic out- 



