54 
NEW OR CRITICAL BRITISH ALGiE. 
served in the Botanical Museum of the University of Christiania, 
made by the late Professors F. C. Schiibeler and M. N. Blytt, 
supplemented by an examination of smaller collections made by 
Prof. Willie and MM. Gran and Hansteen, the author’s own rich 
Herbarium and a small collection belonging to the Museum of 
Bergen having also furnished material for study. 
The first species dealt with is C. tenuissimum , Lyngb., of which 
the author mentions three forms, i.e ., f. arachnoidea , J. A g., 
f. typica , and f. divaricata , Foslie, the last of which M. Foslie 
considers identical with C. divaricatum , Crn. We think it is still 
open to doubt whether the plant mentioned by M. Foslie is really 
the same as that described by the Crouans, more especially as in 
the “ Florule du Finistere ” C. divaricatum is placed in the section 
of the genus bearing immersed sub-prominent tetraspores. We 
are, of course, aware that Gongroceras pellucidum , Kiitz., a plant 
now usually recognized as identical with C. tenuissimum, is also 
placed by the Crouans in the same section, but their figure (tab. 
12, fig. 87 bis.) would lead us to suppose that their C. divaricatum 
was a very much smaller plant than C. tenuissimum , with a 
different ramification. Both Major Beinbold and Mr. Holmes 
understand Crouan’s plant differently from M. Foslie. The 
C. divaricatum of Holmes is seldom an inch high, and comes nearer 
C. diaphanum or C. strictum than C. tenuissimum. Until the 
type specimen described by the brothers Crouan has been examined 
it is impossible to say whether C. divaricatum , Crn., is a distinct 
species, or only a form of some other. Of C. diaphanum , Roth., 
the author admits four forms, f. stricta = C. strictum , J. A g. ; 
f. typica — C. diaphanum , J. Ag. ; f. patentissima , and f. Capri - 
Cornu=C. Capri-Cornu , Farlow. With regard to the first of 
these we cannot agree with the author that it is desirable to unite 
C. strictum with C. diaphanum. In most cases the two species are 
easily distinguishable by their different ramification, and truly 
intermediate forms are very rarely met with. As we have seen no 
authentic specimens of C. Capri-Cornu, we can, of course, give no 
opinion as to whether it is distinct or otherwise. F. patentissima is 
a new form characterised by its patent ramuli, otherwise it 
resembles C. strictum . 
Five new forms of C. circinatum , Kiitz, are mentioned. 
f. tenuis , described as “ much branched, lateral branches usually 
numerous, subdichotomous, the lower part of the thallus 200-300 p, 
the upper 100-150 p thick, attenuated, internodes below and above 
corticated, elsewhere partly corticated or naked.” 
f. genuina. “ Lateral branches few, of uniform diameter, sub- 
dichotomous ; internodes in the lower and upper part of the 
thallus corticated, in the middle portion marked by a narrow 
diaphanous band.” 
i. rigida. “Sparingly branched, lateral branches few, simple; 
lower portion of the thallus 400-500 in diameter ; internodes 
(in the lower and upper part of the thallus) either corticated or 
