spores, lying exposed on the surface of the membrane, and slightly promi- 

 nent, among which are occasionally seen a few short filaments, similar to 

 those that accompany the spores in several other Bictyotece. Substance of 

 the frond delicately membranaceous, closely adhering to paper in drying. 

 Colour a pale olive. Reticulations of the frond large, quadrate. 



As far as the British Flora is concerned, the merit of having 

 discovered this plant belongs to the late talented and indefati- 

 cable Captain Carmichael of Appin, who detected it npon the 

 west coast of Scotland, in the year 1825 or 1826. In 1827 a 

 figure of it appeared in Dr. Greville's ' Cryptogamic Mora'; in 

 1831 it was discovered in Ireland, and in 1833 added to the 

 Flora of Devonshire. But if the very numerous synonymes de- 

 tailed above, and many of which I have transferred from the ex- 

 cellent work of Meneghini, all belong, as there is little doubt, to 

 our plant, it was first observed in the Mediterranean Sea, where 

 it appears to be not very uncommon, in several places. Not a 

 little remarkable, as connected with its Mediterranean habitat, is 

 the fact that so far from its appearing to delight in warm latitudes, 

 the specimens from Scotland and from the north of Ireland are 

 in every respect stronger and more luxuriant than those found 

 on the Devonshire coast. Other circumstances, exclusive of cli- 

 mate, probably influence the growth of this, as of many other 

 Algae, very considerably. Of these the principal appear to be 

 shelter, a quiet sea bottom, and a considerable deposit of alluvial 

 matter. In such localities as Belfast and Strangford Loughs the 

 largest specimens I have seen have been found. One of these, 

 in the possession of Dr. Drummond, is considerably larger than 

 that represented in our figure. 



A second species of this genus, 8. fragilis, J. Ag. will probably 

 be found on our shores. The specimens which I possess, so 

 named by Prof. Agardh, are not in a sufficiently perfect state to 

 enable me to form a decided opinion as to their specific character. 



I regret that our plate has been printed in too dark an ink, 

 an error which was not perceived till the impressions had been 

 struck off. 



Fig. 1. Striauia attenuata ; natural size. 2. Portion of a branch. 3. A 

 portion of the membrane, with a sorus. 4. Spores from the sorus : — all 

 more or less magnified. 



