322 Mr George Traill on the 



134. Callithamniontetragonum (With.), Ag. 



Epiphytic on the larger Algse. Annual. Summer. Eday, fine ; 

 Skaill, West Mainland, fine. There are some very fine Orkney 

 specimens in the Greville Herbarium presented by Mr Pollexfen. 



135. Callithamnion brachiatum, Bonnem. 



Epiphytic on the larger Algae. Annual. Summer. Abundant 

 at Skaill, West Mainland. 



136. Callithamnion granulatum (Duel.), Ag. [Callithamnion spongio- 



sum, Harv. ) 



On perpendicular rocks, and in pools, near low-water mark. 

 Annual. Summer. Skaill, West Mainland, and other places. 



137. Callithamnion corymbosum (Eng. Bat. ), Ag. 



In quiet places at about low-water mark. Always submerged. 

 Annual. June to September. Fruit, July, August. Occurs in 

 considerable abundance in Kirkwall Bay. 



138. Callithamnion seirospermum, Griff. {Seirospora Crriffithsiana 



Harv. ) 



On rocks and stones in deep water. Annual. Summer. Kirk- 

 wall Bay, opposite Crossiecrown, in 5i fathoms, where I obtained 

 it very fine, in fruit, when dredging with Mr William Cowan in July 

 1887. 



In regard to this species Mr Pollexfen writes to me as follows : — 

 " My finest specimens (and they were very fine) were dredged in 

 Kirkwall Bay ; indeed, I doubt whether it has been found elsewhere 

 in Orkney. Some of the specimens Harvey describes as ' more 

 delicate than the Devonshire plant,' and one with ^faveUcv,^ and 

 with the smaller branches chiefly on one side of the larger ones, 

 giving the upper branches a somewhat ensiform appearance, he 

 marks ' Seirospora ? variety or species 1 quite new and curious.' " 



139. Callithamnion versicolor, Ag. 



This Alga was dredged in Kirkwall Bay many years ago by Mr 

 PoUexfen and then identified. The history of its title to be reckoned 

 as a distinct species is curious, and Mr Pollexfen writes to me 

 regarding it as follows : — " Harvey gave it a place in Hooker's 

 British Flora. He afterwards in the Flora Hlhernica describes a 

 variety of Call, versicolor as ^ seiros2)ermu7n, which Mrs Griffiths 

 made a new species, Callothamniou seirospermum (the species 

 immediately preceding), having no doubt of their being quite 

 distinct, and Harvey describes them as distinct species in his 

 Manual of British Algce published in 1841. In an early number 

 of the Phycologia Britannica, pi. xxi., he makes the variety seiro- 

 spermum a new genus — Seirospora Griffithsiana — pointing out the 

 difierence between it and Callitharnnion versicolor, which he stiU 

 speaks of as a distinct species of Callithamnion. Later on, however, 

 when he comes to pi. cclxxii., he describes Call, coryjnbosum, and 

 gives Call, versicolor as a synonym, and states his reasons for 

 considering them identical. It would appear that some modern 



