HuTTON. — On Modifications in Capsules of Mosses. 345 



their points toucTiing or interlaced, so as to form a kind of cage over the 

 mouth which protects the spores from the wind, but allows them to be blown 

 away in small quantities at a time, and by high winds only. In Gonostomum 

 (fig. 5), which inhabits exposed rocks on mountains, this cage is further 

 strengthened by the tips of the teeth cohering together, and this moss may be 

 said to be the type of the group. All these mosses have strong persistent 

 peristomes well calculated to resist the wind, consequently we find that many 

 of them inhabit mountains or subalpine regions, and several grow upon 

 exposed rocks, while in some species of Grimmia only is the capsule innnersed 

 in the perichsetial leaves. The peristome however is not able to protect the 

 spores from the wet, and to accomplish this the greater part have the mouth 

 of the capsule inclined or bent downwards either through the fruit-stalk being 

 curved, or the capsule being cernuous or drooping. I must here remark that 

 the fruit-stalk of Gampylopus is hygroscopic, being curved and burying the 

 capsule among the leaves in dry weather, while when the air is moist standing 

 more erect, an anomaly for which I can ofier no explanation. In Seligeria 

 recurvata the fruit-stalk straightens when dry. 



(6.) In the second group, which is represented in New Zealand by 

 Dawsonia superha and the genera Trichostomum and Tortula, the peristome 

 consists of numerous filiform, slightly hygroscopic teeth, which are either 

 distinct from one another, or united at the base into a membrane. In 

 Trichostomum and Dawsonia superha (fig. 11) the teeth are nearly straight, 

 but in Tortula (fig. 9) they are twisted into a spiral, which in damp weather 

 twists tighter and closer over the mouth of the capsule. The mosses in this 

 group are preeminently inhabitants of the plains, their peristome being too 

 weak and fugacious to withstand the boisterous winds of the mountains. 

 Tortula possesses the strongest peristome, and consequently we often find it 

 growing on walls and other exposed places, while Trichostomum and Didy- 

 modon generally grow on the ground or in sheltered hollows. All have the 

 fruit-stalk elongated, and the capsule erect or nearly so. 



(c.) In the third group the teeth are all more or less hygroscopic, opening 

 when dry and closing over the mouth of the capsule when wet. In some, 

 e.g.y Phyllogonium (fig. 10) and Blindia, the movement is small and the teeth 

 when wet never get beyond an erect position j in others, e.g.^ Fissidens and 

 Gryphcea, they continue the movement until they have attained a horizontal 

 position, and then curl their points inward j in others again, such as 

 Orthotrichum, Zygodon (fig. 3), Eremodon and Fahronia, the movement is still 

 further continued until their backs are adpressed against the outer sides of the 

 capsule. In this group the peristome is beautifully adapted for preventing 

 the spores being dispersed in wet weather, but there is nothing to prevent 

 them being all blown away in one direction by the first strong wind, and we 

 find therefore that they are chiefly inhabitants of the plains, and generally 



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