Clare Island Survey — Marine Algae. 16 135 



perfectly distinct plant, as a synonym. 1 have already pointed out this 

 confusion (Kew Bull., 1909, p. 242); but the following notes, based on 

 observations at Plymouth and in Clew Bay, deal with the subject in greater 

 detail. 



Taking first N. laceration, we find that the variety uncinatum is directly 

 connected with the ordinary forms of this common plant. X. laceratum is 

 (with very rare exceptions) the only species found in rock-pools on open shores, 

 and, though it exhibits great variety of form, there is usually no difficulty in the 

 specific identity of the plant, the iridescent fronds of a pale brick-red or dull 

 purplish-red colour being very characteristic. The uncinate form is not 

 uncommon in pools, being found from early summer till autumn ; it appears 

 to be connected with a more or less vertical habit and contact with other algae, 

 being usually found clinging to Corallina. The hooks may be few or numerous, 

 and terminal or apparently lateral. The form of the frond is very variable, 

 often lobed or bluntly pinnate, but never possessing the definitely acuminate 

 branches of N. uncinatum (Plate X, fig. 11). 



When iV. laceratum occurs in the sub-littoral (1-7 fathoms), the form of 

 the thallus differs somewhat, being longer and more or less regularly 

 dichotomous ; but the iridescence and characteristic dull colour are maintained. 

 Uncinate specimens occasionally occur ; but, except for increased length and 

 greater regularity, they differ little from the rock-pool form. They are clearly 

 connected with the normal plant. Tetrasporic sori are frequent ; these are 

 found, as is characteristic of the species, either in special proliferations or along 

 the margins of the fronds. 



iV. uncinatum J. Ag. is, on the other hand, a plant confined to the sub- 

 littoral region, and, though abundant in Clew Bay, is less generally distributed 

 and apparently very local. It is found in late summer and autumn, being 

 washed ashore in profusion in August, September, and October, in 1909, 1911, 

 and 1910 respectively. It is distinguishable at once by its deep crimson or 

 crimson- lake colour, and lack of iridescence. Most often it is attached to the 

 stems of Laminaria Cloustoni; but it is found on various stiff algae such as 

 Cystoseira, Gracilaria, etc., and by means of its hooked branches is entangled 

 with loose weeds of all kinds. The acuminate character of the branches is 

 always noticeable, but is most marked in young plants. The hooks are formed 

 at the termination of the shoots, but not infrequently new branches grow out 

 below the apex and take on the function of the main shoot so that the growth 

 is sympodial (Plate X, fig. 10). The same course of development probably 

 occurs in N. laceratum var. uncinatum ; but if this be the case, the sympodial 

 growth is more perfect, as the uncinate branches appear merely as small lateral 

 hooks (Plate X, fig. 11). Cystocarps are unknown in N, uncinatum, but 



