MAEINE ALG^ OF THE ' SEALAEK ' EXPEDITION. 129 



monosiplionio brevi tantummodo restante. Thallo sympodiali, radiato ; rainis 

 cum divergentia \. Primo segmento libero raraoruni ad basim satis magnam 

 cellulam incremento basipetali disjungente. Cellulis centralibus magnis, byphis 



merosis ang 



istis cinctis. Sticbidiis ramulis penicillorum sessilibus ; 8-10 sporas 



L 



in unoquoque segmento ferentibus. Cystocarpiis et antheridiis ignotis. 



Coetivy, reef ; in alcobol. 



This new Dasyopsis attains a bcigbt of 2-5 cm., and consists of a small tuft of primary- 

 ascending cylindrical axes or stems, tbat finally become horizontal and give rise to new 

 ascending ones. The tufts, on growing older, become more or less intricate, but I 



■ 



never saw the fronds anastomose. Dasyopsis aperta is a good species for the study of 

 the peculiar Dasyopsis structure, because the cells are large, even at the apex of the 



i 



shoot. It is sufficient to spread the alga on the slide and to tear off carefully with 

 a needle the surrounding penicilli to see plainly the row of central cells, each carrying 

 a pushed aside apex and its first branch whose lowest cell builds up the sympodium. 

 These branches stand spirally around the main axis, as far as I could ascertain, with 

 a divergence of J, and carry long, incurved filaments at their top, which form together 

 the penicillus. The first cell, after the branch has been pushed aside, cuts off a cell at 



base (PL 14. fi 



o 



this is the mother-cell of the downward growing hypha3 



which are at first almost as large as the cells of the central axis or tube. At the top of a 

 stem or axis, where the mutual position of the different cells is still unaltered, the central 

 tube appears to consist of a central and four pericentral cells, but on following the 

 pseudo-pericentral cells to their origin, it will be clearly seen that they are downward 

 growing hyphaj, arising from the first free cell of the pushed aside branch. The sym- 

 podial axis is afterwards covered by a thick layer of smaller hyphoe, which by growing 



between them alter the original position of the cells. 



The stem or main axis is cylindrical, though tapering towards its apex, which is 

 densely covered with penicilli ; these, however, soon fall off, and the base of older stems 

 is almost denuded, though not entirely, for remnants of the basal portion of the penicilli 



often remain. 



The sessile stichidia are borne on the side-brancb cs of the penicilli; they are 

 cylindrical and, when the tetrasporangia have acquired their full size, a little torulose. 

 I counted from 6-8 sporangia in different segments; and the whole is crowned by one 

 or two barren cells. Neither cystocarps nor antheridia were seen. 



There are, according to Palkenberg *, two other species of Dasyopsis, which, like 



D. Stanleyi and D. aperta, have penicilli facing every way, namely l)a,yopsis spinella 

 and I), cervlcornis. Prom the first both D. Stanleyi and i>. aperia differ in the absence 

 of the little spines that have given D. spinella its specific name, and from D 



the shape of their stem, cylindrical th 



SJ 



the inscrtion-pomt 



of the penicilli. 



• Falkenberg, ' Die Ehodomelaceeo des Golfes Ton Ncapel,' 1901, p. 607. 



SECOND SERIES.— BOTANY, VOL. VIII. 



IT 



