Clare Island Survey — Marine Algae. 15 137 



p. 30). 1 It was transferred to Laurencia by Lenormand in 1830 (Duby, 

 Bot. Gall., p. 951); and his name has been used by Kiitzing, J. Agardh, 

 Le Jolis, and De Toni. Dawson Turner in 1808 named the plant L.pmna' 

 tifida var. angusta, giving a figure (Synopsis, PL 20, fig. /), and quoting 

 L. hybrida as a doubtful synonym. Turner's name was adopted by Greville 

 (who gives an excellent figure), Hooker (Brit. Flora), and Harvey (Manual 

 Ed. I, p. 69, and Phyc. Brit., PL 55). The ideas of these writers as to the 

 plant were not very exact, and they confused it with narrow forms of L. pinna- 

 tifida. A third name (and one which has been largely used in this country) 

 is L. caespitosa Lamx., which dates from 1813. This, however, was a nomen 

 nudum, and was moreover reduced to a synonym of L. dasyphylla by C. Agardh 

 in 1822. But in 1840 it was taken up by Montagne (for a plant which he 

 afterwards decided was a new species, L. canariensis, PL Crypt. Can., p. 154, 

 and Kiitz., Spec. Alg., p. 854), and was used by Harvey in the second edition 

 of the Manual and also in Phyc. Brit. (PL 286). Our plant, therefore, 

 figures in the latter work under two names; and Harvey himself admits doubts 

 as to the species. J. Agardh, at a later date, examined some of Lamouroux's 

 specimens, and redescribed what he considered the true L. caespiiosa Lamx. ; 

 the identity of this plant is, however, doubtful. Though most of the older 

 writers confused the species with narrow forms of L. pinnatifida, the plant 

 they had in mind is perfectly clear, both from their descriptions and from 

 specimens in herbaria. Some have used one name, some another. The name 

 hybrida (1805) has priority over caespitosa (1813), which, as we have seen, was 

 merely a nomen nodutn till 1840. There is no question that the plant is 

 distinct from L. pinnatifida. 



Description and Habitat. — L. hybrida is abundant on the British shores and 

 forms part of the Gigartina-Laurencia association of exposed coasts, but it is 

 also frequent in rock-pools. It may always be distinguished from L. pinnatifida 

 by the constantly cylindrical fronds and its pyramidal outline. The small size, 

 greenish colour, and caespitose habit are also noteworthy, whilst its marked 

 winter growth and absence in summer are quite characteristic. Small sporelings 

 2-3 mm. high are discernible in September ; these develop during autumn and 

 winter, and fruit in early spring. By May the plant begins to disappear, and 

 is not seen again till September or October. When growing on bare rocks 

 which are left dry by the tide, the plant is very compact, and seldom more 

 than 1-2 inches high ; but in shallow pools fully exposed to the light, it is more 

 lax, and may attain a height of 4-5 inches. In autumn and winter L. hybrida 

 is a dark greenish purple; but with the advance of spring the purple hue 



1 In some copies of this work the date is erroneously stated to be 1815. 

 R.I. A, PROC, VOL. XXXI. S 15 



