THE BRYOPHYTA OF ICELAND 477 



\vhich may be almost as large as, for instance, that in B. rclnsiim. It is, 

 however, not usual for the thickening to he distinctly localized around 

 the base of each individual peristome tooth; it has more the charac- 

 ter of a continuous ring, 0.020.07 mm. broad. Hagen (Musci Xorv. Bo- 

 realis, p. 141) pronounces the opinion that ultimately all the species with 

 a distinct fundus will be united together in a separate group in a na- 

 tural system of species of Brynin (Brya hcemotostomata). The feature 

 in question appears, however, to be too variable for that purpose. It 

 is especially in the group of forms of inclinatum that this peculiar de- 

 velopment of the peristome base occurs, but it is also met with in 

 other groups, although less frequently, for instance in B. pnrpnrascens 

 where it may be almost as large as in Brya hcemotostomata Hagen) 

 and in B. uliginosum. B. ciirvatnm Kaur. & Arnell, which Hagen refers 

 to B. hcematostomata, also belongs to the piirpnrascens p aliens group. On 

 the other hand, forms mav also be met with in which the fundus is 



t/ 



rather slightly developed or even quite wanting, for instance B. Kan- 

 rim, B. retnsnm and B. Graefiannm, referred by Hagen to B. hcemato- 

 slomata. This diminishes the value of the character in question, and 

 it does not appear to have greater systematic importance than has* the 

 peculiar structure of the lamellae for the group Hemisynapsium, which 

 structure is especially met with in the group of species in which the 

 fundus formation occurs. Both the fundus formation and the indentation 

 of the lamellce, as also the occurrence of perforations in the median 

 line of the peristome teeth, are probably connected with certain external 

 influences, and are very often met with together. Here it is especially 

 the degree of salinity of the substratum which is of importance, aula- 

 codonte peristomes being found almost exclusively in Brynm forms 

 collected from localities close to the coast, while forms with a distinct 

 fundus-formation, although most frequent in the vicinity of the sea, \ r et 

 have also been found far inland, or at a height of 400500 metres 

 above sea-level. In Iceland indented lamella? and peristome teeth more 

 or less perforated in the median line have been observed in forms of 

 B. inclinainm, B. retnsnm, B. archangelicum, B. calophyllnm and B. pnrpur- 

 ascens, in the last-mentioned species, however, the peristome teeth are 

 never perforated. 



The spores vary somewhat in size, most frequently 0.0220.025 mm., 

 more rarely as much as 0.029 mm. 



Brynm lapponicnm Kaurin has not been found in Iceland, but forms 

 which approach this species by having broader and longly decurrent 

 leaves are rather frequent. 



139. Bryum retusum Hagen. 



N. Iceland: Hnausar in Vatnsdalur!; Yidiimri!; W. Iceland: Stykkis- 

 holmur!; Borgarnes!. 



This species grows on peat or soil-covered rocks. The capsules 

 ripen in the beginning of July. Near Stykkisholmur they were almost 

 ripe on June 15th. In all the plants referred to this species the leaves 

 were shorter and broader than in B. inclinatum, with the nerve vanishing 

 in the apex and shortly excurrent in the perichaetial leaves. The capsule 



