162 



IK Lille Middelgrund, 17—19 m, 61 cm; IH, south side of Lille Middelgrund, 20-28 m; ER, Fyrbanken 

 east of Aniiolt, 23 m, 28 cm; lA, Store Middelgrund, 16,5 m; same locality (Borgesen); off Gilleleje, 12 

 miles from land (Lyngbye); Nakkehoved (Lyngbye). — Sii: Washed ashore at Hellebaek (Rasch, B0rgesen), 

 29 cm, and north of Helsinger (Steenberg, C. Rosenberg, !) 26 cm, bM, south of Hveen, 22,5 m, loose, 40 cm. 



Fam. 5. Nemastomataceae. 

 Platoma (Schousboe) Schmitz. 

 1. Platoma Bairdii (Farlow) Kuckuck. 



p. Kuckuck, Beitrage zur Kenntn. d. Meeresalgen. 12. Ueber Platoma Bairdii (Farl.) Kck. — Wissensch. 



Meeresuntersuch. Neue Folge. V. Bd. Abt. Helgoland, Heft 3. 1912, p. 187—203. Taf. IX— XL 

 Nemastoma (?) Bairdii Farlow, Proceed. Amer. Acad. Arts and Sciences, 1875, p. 351 ; Mar. Alga; of New 



England, 1881, p. 142; Batteus, Cat. Brit. Mar. Alg., 1902, p. 94. 

 Helminthocladia Hiidsoni Batters, Journ. of Bot. 1900, p. 377. Tab. 414 fig. 15-16, non J. Agardh. 



In July 1915 I found by dredging in Lille Belt some small specimens of this 

 interesting Alga, hitherto only recorded from three widely remote places (coast of 

 Massachusetts, coast of Northumberland and Helgoland). As the structure and de- 

 velopment of the species have recently been exhaustively treated by Prof. Kuckuck, 

 I shall only make some few remarks upon the Danish specimens, referring for the 

 rest to Kuckuck's excellent description. 



The plant forms small bundles on a granitic pebble, each given off from a 

 well developed basal disc, and reaching only a length of 1 cm. The upright fronds 

 are more or less branched, rarely unbranched, terete, or the thickest fronds some- 

 what Hattened. As shown by Kuckuck, the frond branches by dichotomy^, but one 

 of the shoots produced by the division often becomes more vigorous than the other, 

 and the ramification then seems to be lateral. Hyaline hairs were not met with; 

 according to Kuckuck their occurrence is variable. 



The plants bore either tetrasporangia or carpogonia and cystocarps, while 

 anlheridia were not met with either here or at Helgoland. The two kinds of indivi- 

 duals were quite distinct; no carpogonia were observed in the tetrasporiferous speci- 

 mens or vice versa (comp. Kuckuck 1. c. p. 192). The emptied sporangia were fre- 

 quently replaced by a sporangium produced from the subjacent cell. "Prospory" 

 0: production of sporangia from the basal disc, was not met with in the Danish 

 specimens. 



Locality. Lb: At Lyngs Odde, right opposite Middelfart, stony bottom, about 20 meters depth. 



1 Kuckuck thinks (1. c. p. 190) that the dichotomy in this plant is only apparent, as it cannot be 

 derived from a longitudinal division of the apical cell. This, however, must be considered a too nar- 

 row definition of the conception of dichotomy. In my opinion, dichotomy exists in all cases where 

 the growing point divides into two equal parts by a vertical dividing plane or furrow, the two parts 

 at first diverging equally from the original direction of growth, no matter whether the growing point 

 consists of a single cell (Dictijola) or of several cells (Furcellaria, Lijcopodium, Selaginella, roots of 

 Isoctes etc.) or is a part of a coenocj'tie organism [Thamnidiiim, Piptocephalis) . 



