1863.] MARINE ALG^ FOUND AT BRIGHTON. 517 



31st of October^ 1861, many fronds, considering the general 

 scarceness of the plant, were thrown on the beach. The plant is 

 known to grow both to the east and west of Brighton, but the 

 habitat is seldom accessible to the algologist. A few years ago, 

 Mr. Pike tells me he waded out as far as some Codium bursa 

 which he saw growing ; the fronds were then about the size of 

 nuts. Being so small, he would not gather them then^ hoping to 

 return for them when sufficiently grown. In the meantime 

 heavy gales came on, and loosened and dispersed the plants, and 

 he thinks broke up the habitat. After that, Codium bursa was 

 scarce for some time, 



Codium bursa grows on chalk rock, on barnacles, mussels, 

 oysters, Pecten opercularis, and pebbles. It is generally entangled 

 with Rytiphlcea pinastroides, and I have found growing on it 

 young plants of Sphacelaria Sertularia and S. plumosa/^ and 

 also the zoophyte Sertularia argentea. 



The plant grows sometimes in single fronds ; sometimes two, 

 three, and even seven and eight in a group, and adhering to 

 each other ; only one of the fronds being immediately attached 

 to the rock. Hence we learn that every part of the frond is 

 prolific. The appearance of one of these heaped specimens 

 is somewhat like the figure in the ' Phycologia Britannica' of 

 Leathesia tuberiformis , except that the point of attachment is 

 smaller. In no case have I ever seen a specimen Mith a wide 

 base like the figure of Codium bursa in the ' Phycologia.^f The 

 point of attachment is always small. When one frond grows 

 upon another, which is often the case, the junction is formed by 

 interlacing fibres, so strong that it requires some force to sepa- 

 rate them. 



In form, Codium bursa is generally spherical, and always 

 hollow. In young and fresh specimens the substance is thick, 

 firm, and crisp ; with age it becomes thinner, and at last an 

 opening is made; hence its name bursa (a purse). After expo- 

 sure, specimens are frequently found collapsed; at other times 

 they are much lacerated, and acquire a flat shape; hence an- 

 other common appellation, sea flannel, which gives a very good 

 idea of the occasional appearance of the plant. 



* Now Chcetopteris jplumosa. 



t I believe that what appears to constitute the wide base in the figure, is merely 

 a collapsed frond. 



