208 SUMMARY OF CURRENT RESEARCHES RELATING TO 



examined, but the authors show that its presence is not destructive to 

 marine algae. 



Sphaeranthera lichenoides.*— F. Heydrich discusses this plant, which 

 was figured so long ago as 17*6 by Ellis and Solanderf; indeed, their 

 figures are pronounced to be far the best existing to this day. He 

 criticises adversely the views held by Foslie on the limits of the species 

 and its forms, which views have been incorporated in De Toni's Sylloge 

 Algarum. Heydrich considers that of the material he has examined, two 

 large groups can be made; the first, consisting exclusively of plants 

 which grow on Corallina, and are found more often on the North- 

 European coasts ; the second, all those which do not occur on Gorallina, 

 but on stones, large algaB and rhizomes of Posidonia, and inhabit the 

 Mediterranean. The first form he calls pusilla, the second depressa. 

 The figure of Ellis and Solander \ represents Heydrich's f . pusilla, but 

 f . depressa has never been figured. A third form, growing on Rytiphlaza 

 pinastroides in Jersey is called f . densa and forms a link between S. lichen- 

 oides and 8. Philippi. The manner of attachment to the substratum is 

 discussed and the differences are considered by the author to be of value 

 in the determination of the species. The structure of the procarp is 

 considered in detail, and both antheridia and tetrasporangia are 

 described. 



Fucus Living on Sand and on Mud.§— C. Sauvageau has found 

 two species of Fucus — F. spiralis and F. vesiculosus — growing at Arcachon 

 on clayey sand. The plants of F. spiralis measure only a few centimetres, 

 rarely a decimetre. The older plants throw out at their base new fronds 

 on a very short perennial stipe, but these shoots never become trans- 

 formed into stolons. Propagation takes place exclusively by the germi- 

 nation of oogonia. The plants are attached to the sand by means of 

 rhizoids, which are the prolongation of the intertwined hypha? or fibres 

 of the stipe ; these become generally welded together to form the disk 

 of attachment in plants of Fucus which have passed their first youth. 

 Thus it is seen that F. spiralis adapts itself to a life on sand by preserv- 

 ing the characters of its early stages. Living side by side with F. spiralis 

 is found F. vesiculosus, similarly affixed to the sand by a bouquet of 

 rhizoids. It attains, however, a greater height, namely, 10-15 cm., and 

 it grows more rapidly. The large fronds are usually without vesicles, 

 and the few vesiculiferous individuals observed were not fertile ; indeed, 

 the fructification, almost constant in F. spiralis, is on the contrary rare 

 in F. vesiculosus growing on sand, while large plants of this species fixed 

 on a solid base are abundantly fertile. 



The author records also F. lutarius, growing on stretches of mud at 

 a tide level intermediate between that of F. vesiculosus and F. platycar- 

 pus var. spiralis (F. spiralis), forming scattered tufts which are weighed 

 down at low water. Their base, more and more enveloped in mud, is 

 never fixed to any solid substratum, and new fronds arise from the 

 midrib of the enveloped portion. Thus the plants multiply by vegetative 



* Beih. Bot. Centralbl., xxii. Abt. 2 (1907) pp. 222-30 (1 pi.). 



t Zoophytes (London, 1786) p. 131, tab. xxiii. (figs. 10-12). 



j Loc. cit. § C.R. Soc. Biol. Bordeaux, lxii. (1907) pp. 699-703. 



