344 Transactions. — Botany. 



the wind'; wliilc in some species of Gymnostomum, as well as in Caloynnion, a 

 further provision is made by the walls of the capsule being much thickened at 

 the mouth, which reduces the size of the opening. In most of those genera in 

 which the apparatus for protecting the spores is more perfect this annulus falls 

 away* after it has performed its office of throwing off the operculum from the 

 capsule, but in the genera just mentioned it is pei'sistent.t 



In (Enectangium also the spores are very minute and numerous, which gives 

 evident facilities for their far and wide dispersion:}; 



2. Mosses in which the peristome is used. 



I come now to that large division of mosses which have a series of teeth, 

 called the peristome, arranged round the mouth of the capsule. In its most 

 complete state this peristome consists of an external row of sixteen conical 

 teeth, and an internal folded membrane divided above into processes sometimes 

 with cilia between each (fig. 7). The inner peristome is, however, variously 

 modified, and is often altogether absent. The outer peristome consists 

 normally of sixteen teeth, which are sometimes split half way down, as in 

 Dicranu7n, Fissidens, etc. Sometimes they are divided to the base so as to 

 make their number thirty-two, as in Trichostomum and Tortula. In rare 

 cases also two teeth are joined together so as to reduce their number to eight, 

 as in the tropical genus Octohlepharunif while occasionally they are reduced to 

 four, as in Tetraphis. 



The peristome also is very variously developed in different mosses. In 

 some, such as Weissia^ Didymodon, Conomitrium^ etc., the teeth are short and 

 fragile and soon break off. In Trichostomum, Encahjitta, etc., they are 

 stronger ; while in most genera they are strong and answer admirably their 

 purpose of preventing the too easy escape of the spores. 



These mosses can be divided into five groups in each of which the peristome 

 is used in a different way. 



(«,) The first group, which is represented in New Zealand by the genera 

 Dicranum, Dicranodontium, Campylopus,Racomitrium,\\ Leucohryum, GHmmia, 

 Ceratodon, Conostomum, and Symhlej)haris, have the peristome long and well 

 formed, and the teeth stand nearly erect round the mouth of the capsule with 



* SymhUpharia is an exception. 



+ Braclnjodus might l)e placed here, for its peristome being shorter than the amiulus, 

 it cannot in any way affect the dispersion of the spores. 



X I have not, however, been able to trace any connection between the abundance or 

 rarity of a moss and the size of its spores. For instance, the spores of J/i/pnuui 

 cuprcssiforme and //. nitahulum are nearly twice the diameter of those of //. pi-aloixjum 

 and Jl. confcrtuin, while //. triquetrum and II . jmruiii hold an intermediate position. 



II In Eacomitrhnn ociculare the teeth are sliglitly hygro8coi)ic, sprcadinc when dry, 

 but erect and slightly incurved when wet. 1 liave noticed that in species a sticky 

 8u])8tance is found amongst the spores, which is drawn out into lines like cobwebs 

 between the teeth, and by this means the spores arc often stuck on to the inner side of 

 the peristome. 



