112 



The above diagnosis is made after specimens growing on Porphyra umbilicalis 

 in tlie harbours of Skagen and Frederilishavn. Tiiey are somewhat more branched 

 than f. luxurians and have a little thinner filaments and shorter cells. The spor- 

 angia are very numerous and, at least in many specimens, all tetrasporous. They 

 are in a great measure placed on branchlets which are usually opposite, partly 

 also sessile on the sides of the filaments. From the characters mentioned this 

 form is, in spite of its great resemblance, so difl'erent from the main form, that I 



was for some time inclined to regard it as a 

 distinct species, but some other less pronoun- 

 ced specimens have led me to the result that 

 it is closely related to the f. luxurians and 

 still more to the f. secundata. Thus I found 

 at Middelfart some specimens having chiefly 

 monosporangia, 16 — 20 a long, 11 — 13, « broad, 

 but also some tetrasporangia , and the spor- 

 angia were placed on the filaments as well 

 as on the branchlets. These specimens might 

 be regarded as intermediate between f. lux- 

 urians and f. tetrica, but they were also re- 

 lated to f. secundata, differing however by 

 longer cells (3 — 5 diameters long). The re- 

 semblance between the f. tetrica and f. secun- 

 data will be seen on comparing fig. 38 with 

 fig. 39. To this form at least some of the 

 Faeroese specimens mentioned by Borgesen 

 (I. c. fig. 53) may be referred. 



Only found in summer, the typical spec- 

 imens growing on Porphyra umbilicalis. 



Localities. Kll: Harbours of Skagen and Frede- 

 riksliavn. Sa: Middelfart, on Cladophora. 



Fig. 39. 



Cliantransia virgatula secundata. Plants growin<< 

 on Porphyra umbilicalis at Kshjei g. A and B. bran- 



secundata (Lyngb.). 

 Callithamnion Daiviesii ft, secundatum Lyngb. Hydr. 



p. 129 tab. 4!. 

 Acrochcetiiim secundatum N;eg. Beitr. Ceram. p. 405. 



du el filaments with monosporangia. r and /J, young Chantransia secundata Thur. in Le Jol. Liste p. 106; 



plants. 2(i0:l. Borgesen, M. A. F;er. p. 350 ; Kuckuck in Oi-tmanns, 



Morph. Alg. I p. 650; Kylin (1907) p. 115. 



That Ch. virgatula and C/i. secundata are nearly related and often difficult to 

 distinguish from each other tias often been admitted, also by Borgesen and Kuckuck, 

 who think however that for the present they ought be kept distinct (Bgrgesen 1. c. 

 p. 354). I have also wished to regard Ch. secundata as a distinct species, but I have 

 ended by referring it as a form to Ch. virgatula, as the limit between them, accor- 

 ding to my experience, cannot be drawn without arbitrariness. As mentioned above, 



