OCCUKKFNCK OF PYLAIELI .1 I'AIUA IN SCOTLAND 103 



sometimes only the terminal cell was developed into a zoospor- 

 angiuni. By this fruit it is at once distinguished from 

 Ectocai'pns distortiis, Harvey, which it so exactly resembles 

 in habit that by the naked eye it would be almost im- 

 possible to say to which species a plant might belong. 



The occurrence of l\ varia on the coast of Scotland is 

 interesting for three reasons : 



1. It is one more addition to a numerous series of the 

 algre of Scandinavia that have been detected on the coast of 

 Scotland, in consequence of a definite search for Norwegian 

 species which I started some years since, and which has 

 resulted in the discovery in Scotland of a large number of 

 species new to the British Flora by several algologists, more 

 especially Mr. G. W. Traill of Edinburgh and Mr. E. A. 

 L. Batters. 



2. It is one of the forms characteristic of species grow- 

 ing amongst Zostera roots, in water comparatively still and 

 less saline than ordinary sea water. Under such conditions 

 there appears to be a tendency to the horizontal development 

 of shorter branches, as in Ectocarpus distortus, E. Landsburgii. 

 Sphacelaria cirrJiosa, var. patentissiina, Ilalopteris filicina, f, 

 patens (S. Sertularia, " Phyc. Brit."), and Laurencia obtusa, 

 Lamx., f. crucifera, Hauck. 



3. It is variously described by different algologists : by 

 some as a species, and by others as a variety. 



Dr. Kjellman, who first published it as a distinct species, 

 still maintains its specific rank in the " Handbok i Scandin- 

 aviens Hafsalgflora " (1890), p. 83. 



Dr. Kuckuck, in an inaugural dissertation entitled "Beitrage 

 zur Kenntniss einiger Ectocarpus Arten der Kieler Eorde," 

 degrades it to a sub-species ; considering that Pylaiella litoralis 

 consists of a series of forms (fonnenkreis}, modified accord- 

 ing to the circumstances under which it grows. This species 

 he divides as follows : 



Pylaiella litoralis, Kjellm. 



Sub-species a, oppositus. 



f. typica> Kuck. (E. firnuis f. vernal is., 

 " Aresch. Alg. Scand. Exs." Ease. 

 4, No. 173. 



