566 G. T. HARRIS ON 



I myself have never seen Schistostega in such a markedly mari- 

 time station. Mr. Michael adds that he collected some of the 

 growth both from the sides and from the pools, but found only 

 Diatomaceae. This, however, does not disprove the presence of 

 the moss, as its minute fronds are extremely delicate and would 

 easily be rendered unrecognisable in a heterogeneous mass of 

 material. 



The fruit appears to be somewhat rare, though when fertile 

 the capsules are often produced in abundance. A great help 

 in the distribution of the plant is afforded by the extremely 

 deciduous nature of the capsule, brought about by the structure 

 figured in Plate 23, fig. 3, and which appears to have escaped the 

 notice of bryologists, as I have seen no reference to it in any 

 4iterature I have consulted. The perichaetium in Schistostega is 

 stalked, unlike the majority of mosses in which it is sessile ; the 

 proximal end of that portion of the seta bearing the capsule, and 

 which is the true seta, is bulb-shaped and composed of large 

 irregular cells. This bulb-like portion fits in the hollowed recep- 

 tacle of the vaginula, the whole forming a ball-and-socket arrange- 

 ment. When the capsule is mature the large spongy cells at the 

 base of the seta contract, causing it to fit so loosely in the vaginula 

 sheath that a very slight touch is sufficient to dislodge it. Quite 

 early in the life of the sporogonium, even before the rupture of 

 the venter, the ball-and-socket arrangement has already been 

 formed (Plate 23, fig. 4), and the seta may easily be forced away 

 from the vaginula by placing a cover-glass over a female plant 

 and applying a little pressure. Only one archegonium is present 

 in the female plant, and there are no paraphyses. A further aid 

 in the distribution of the plant is the presence of abundant 

 gemmae, which obviously are easily conveyed by the fur of rabbits 

 from one burrow to another. It is very curious that these 

 gemmae have hitherto escaped notice in this country. I myself 

 never noticed them in any gatherings until the autumn of 1917, 

 when I first found them abundant in some gatherings made on the 

 moor near Lydford, and correspondents who have at my request 

 specially examined their gatherings for their presence write saying 

 that they have failed to find any. 



My observations suggest the conclusion that these gemmae 

 Are principally produced when barren conditions of the plant 

 prevail ; although they may be present in fruiting commuiuties. 



