49 



ON CERTAIN GALLS in FURCELLARIA amd CHONDRUS. 

 By Ethel S. Barton. 

 (Plate 418, figs. 1-6.) 



The subject of gall -formation in algse, as the result of attack by 

 animals, has never received much attention, though the interest of 

 such a study should attract both zoologists and botanists. Up to 

 the present the only instances recorded are those on Vaucheria 

 caused by a rotifer'-'; on Rhodymeniapahiiata Grev.t and Desmarestia 

 aculeata Lam.]: by a copepod ; and on AscopJiylluni nodosum Le Jol.| 

 by a nematode worm. It may be remembered that the nematode of 

 Ascophyllum was not only new to science, but was the first and 

 hitherto the only recorded marine species. In this paper two more 

 instances are described in which algae produce galls, as the result of 

 attack by nematodes. 



In May of this year it was observed that a considerable number 

 of plants of Fiucellarid fastigi/ita, thrown up on the shore at Lyme 

 Regis, showed irregular swellings along the thallus, and on investi- 

 gation these swellings proved to be galls inhabited by nematodes. 

 Somewhat similar outgrowths were also observed on Chundrus 

 crispus, though very sparingly. Specimens of these al^ae have 

 been sent to Dr. de Man for determination of the nematode, and 

 he reports that in neither alga does he find the Tylenchus fucicola 

 which inhabits Ascophyllum. It is difficult to say as yet whether 

 the nematodes found in Fuicellaria and Chondnis are identical 

 species, but in any case they belong to a genus other than Tylenchus. 

 A description of them will be published later by Dr. de Man. 



The Furcellaria galls were present in so much greater abun- 

 dance than those on Chondrus, that it was possible to work them 

 out more satisfactorily. The general development of the outgrowth 

 in Furcellaria is much the same as that in Ascophyllum. In the 

 youngest stages observed, the peripheral cells and the layer im- 

 mediately below these are disturbed and forced asiuider by the 

 entrance of the nematode, which is found sometimes near the 

 opening, sometimes as deep down as the centre of the thallus. 

 The peripheral cells of the thallus round the point of entrance 

 begin to divide transversely, parallel to the surface, and grow out 

 above the level of the surrounding cells ; thus forming a small 

 excrescence, the first beginning of the gall. At this stage certain 

 of the cells situated below the excrescence are to be found closely 

 packed with rather large granules, to be described later. The gall 

 continues to grow by subdivision of its outermost cells, while the 



* Vaucher, Conferves d'eau douce, t. iii. fig. 8 (1803). 



t E. S. Barton, " On the Occurrence of Galls in Rliodymenia palmata 

 Grev.," Journ. Bot. 1891, 65, t. 303. 



X E.S.Barton, "On Malformations of Ascophyllum and Desmarestia,^^ 

 in Phycological Memoirs, p. 21, t. vii. April, 1892. 



Journal of Botany. — Vol. 39. [Feb. 1901.] e 



