Contribution. I. 131 



Spongomorpha centralis Kiitz. 1. c. t. 80. 

 Exsicc. Conferva arcta Aresch. Alg. Scand. exsicc. Nr. 129. 

 Cladophora arcta Aresch. 1. c. Nr. 334 et 335. 

 Spongomorpha arcta Wittr. et Nordst. Alg. exsicc. Nr. 114, 316? 



413, 612. 

 Conferva centralis Wyatt, Alg. Danm. Nr. 46. 



f. penicilliformis Fosl. 



in Wittr. et Nordst. Alg. exsicc. Nr. 613. 



f. Sonderi Kiitz. (nob.) 



Spec. Alg. p. 419. 

 Desor. Spongomorpha Sonderi Hauck, Meeresalg. p. 444. 

 Fig. „ ., Kiitz. Tab. Phyc. 4, p. 79. 



f. hystrix Stromf. (nob.) 

 Descr. Spongomorpha hystrix Stromf. [si. Algveg. p. 54. 

 Syn. Conferva arcta Lyngb. Hydr. Dan. p. 157. 

 * centralis Lyngb. 1. c. p. 161. 



I have taken the above mentioned typical form in a 

 rather wide sense. Probably it may be divided into two 

 subforms, a stricta and $ centralis. Most nearly related to 

 it is, on the one side, the form that I have distributed in 

 Wittr. et Nordst. Alg. exsicc. Nr. 614 under the name 

 of f . pulvinata. It is easely recognized by its mode of growth, 

 and very numerous rhizoids connecting the particular branch- 

 systems into dense masses. It often forms coherent mats 

 spreading widely over sandcovered rocks. I have seen such 

 mats several hundred square foot in extent by a thickness 

 of 4 — 8 cm., and the surface sometimes almost plain. On 

 the other side, the form penicilliformis is characterized by 

 its penicillated or thinly clustered frond, the branches being 

 erect and rather rigid, in the lower part of the frond loose- 

 ly connected by numerous rhizoids. The main axis is at the 

 base usually thinner than higher up, in the middle 100 — 140 

 \i thick, and chiefly upwards bearing pretty few elongated, 

 erect branches. The cells are generally 1—2 times more 

 long than thick. The rhizoids, by this form only appearing 



