INTRODUCTION TO CRYPTOOAMIC BOTANY. 221 



lar lateral appendages. In tliis species and some others, as 

 Alaria Pylaii and Laminar ia reniformis, there is a very 

 beautiful hexagonal tissue, remarkable for its extremely thick 

 lining substance, which in some cases almost obliterates the 

 cavity. I have observed it in A laria esculenta, but it is much 

 more regular in the two species above mentioned, as appears by 

 sketches from Dr. Hooker now before me. Echlonia, unlike 

 Laminaria and the genera formed from its species and their 

 allies, is essentially a genus of the south, though one species 

 ascends as high as Spain and the Canaries. The frond is pin- 

 natifid, the pinnre arising from the evolution of the marginal 

 teeth. The stem of E. huccinalis is three to four inches 

 thick, and strongly inflated above. 



204. Tlialassiophyllum Clathrus is one of the most beau- 

 tiful productions of the sea, and, like so many other fine allied 

 seaweeds, is a native of the Russian coast of North America. 

 " It is generally about the height of a man, very bushy and 

 branched, each branch bearing a broad leaf at its extremity, 

 which unfolds spirally, and by this gradual development pro- 

 duces the stem with its branches and lateral divisions. A 

 spiral border wound round the stem, indicates the growth of 

 the frond. The frond presents a large convex bent lamina 

 without nerves ; or a leaf of which one half is wanting, for the 

 stipe may be considered as an excentric nerve. A number of 

 rather long narrow perforations, arranged in a radiating form, 

 gives it the appearance of a cut fan ; these foramina being 

 coeval with the formation of the frond, and apparently not 

 owing to inequalities of substance."'* 



205. Costaria contains one, or perhaps two, remarkable 

 species, differing from Laminaria, in having from three to 

 five ribs radiating from the tip of the stem, and nmning 

 almost parallel, like those of many endogens. This genus, as 

 far as is at present known, is confined to the north-west coast 

 of North America. The Lessonice (Fig. 16) are amongst the 

 most wonderful Algre, being, in fact, large dichotomous trees, 

 with leaves growing above, and hanging do-\vn one to three feet 



* Merteus, 1. c. See Hook. Bot. Misc., vol. 3, p. G ; Liun., v. 4, p. 49 



