248 



Cavers : Notes on Yorkshire Bryophytes. 



above the insertion of the stalk, soon becomes filled with starch, 

 to be used in the development of the sporogonia. Should none 

 of the archegonia be fertilised, the apex of the branch resumes 

 its g-row^th, leaving behind the withered receptacle as a brownish 

 prominence on the upper surface of the thallus. An abortive 

 receptacle of this kind shows the characteristic barrel-shaped 

 pores and the withered archegonia, but bears no rhizoids. 



In a fertile receptacle the stalk grows actively for a time, 

 the cells dividing repeatedly and showing a fairly regular arrange- 

 ment in longitudinal rows. Some of the ribbon-like hairs are 

 carried up at the top of the stalk, the rest remain at the base of 

 the latter. The growth of the stalk then ceases for a time, 

 whilst the development of the sporogonia proceeds actively. 

 Fertilisation occurs in July and August, according to the writer's 

 observations, and the ripe capsules open in many cases as early 

 as March, though in plants growing in exposed and elevated 

 situations this does not take place until as late as June. The 

 dehiscence of the capsules is preceded by the elongation of 

 the receptacle-stalk, which has hitherto remained very short. 

 (Fig. I, D.). This elongation, which takes place in a few days, 

 is due simply to great increase in length of cells already formed. 

 The cells of the stalk at first contain numerous small starch-grains, 

 which are used up during this sudden growth in length. After 

 the receptacle has thus been carried up to a height of from 2 to 

 5 cm., and the capsules have opened and shed the spores, the 

 delicate receptacle-stalk soon droops and collapses, and with 

 the receptacle itself becomes withered. 



Fertilisation. — The antherozoids set free from the ripe 

 antheridia require water in which to travel towards the arche- 

 gonia, and the latter also need water in order that their necks 

 may open to allow the entrance of the antherozoids. As might 

 be expected, therefore, fertilisation seldom occurs in plants which 

 are not supplied with water.'" Each male cell or antherozoid 



*It is ver}^ probable that insects play a part in bring-ing- about the 

 fertilisation of both liverworts and mosses, by crawling- over the plants and 

 transferring- water with antherozoids to the female plants, in the case of 

 dioecious species. The explosive discharg-es of antherozoids, already 

 mentioned, doubtless also serve to this end, the spray shot up in these 

 discharg-es may be carried by air-currents to the neig-hbourhood of the 

 archeg-onia. Discharg-es of this kind occur in several other thalloid liver- 

 worts, and they have been described by the writer in two recent papers 

 ('Annals of Botany,' Vol. 18, 1904, pp. 87-120; 'Torreya,' Vol. 3, 1903, pp. 

 179-182) where the literature of the subject is given. But of course, in 

 g-eneral, the required moisture will be furnished by rain or dew covering- 

 the plants, and the special means of effecting fertilisation just mentioned 

 w^ill only come into play during- dry weather. 



Naturalist, 



