THE BRYOPHYTA: HEPATICAE, THE LIVERWORTS 409 



no distinction between capsule and seta, and they mature progressively from 

 the apex downwards. 



This very small order, which embraces only four genera, is important 

 because of its isolated position among Bryophyta and because some botanists 

 have seen in it a presage of the independent sporophyte which is characteristic 

 of the Pteridophyta. The plants are all small thalloid types, living under 

 very moist and shady conditions, and none of them is common. Anthoceros 

 itself is the best known, and we will confine our remarks to it. 



Anthoceros laevis 



There are six species of Anthoceros in Britain, all rather similar, among 

 which our species may stand as a type. It is widely distributed, especially 

 in the west and north, but is nowhere common, though when found it may 

 be locally very abundant. It grows on moist soil, on the sides of shady 

 ditches or in moist hollows among rocks. The plant is the gametophyte 

 and forms a small, dark-green, translucent thallus, 5 to 15 mm. across, 

 divided into smooth, broad lobes, with the margins crenate, that is to say, 

 formed of small rounded lobe-segments (Fig. 392). The sporogonia are long, 



Fig. 392. — Anthoceros laevis. Plants with mature sporogonia. 



Natural size. 



delicate, green structures, like blades of grass, which grow in clusters from 

 the back of the thallus, usually in the winter months. The species is 

 dioecious, male and female sex organs being on separate plants. 



Anthoceros is able to absorb water all over the surface of both gametophyte 

 and sporophyte. The water rises over the edge of the thallus on to the 

 dorsal surface and thence to the sporogonium. A slow conduction takes place 

 internally from the foot of the sporogonium, but it is of minor importance 

 compared with the external conduction. 

 14 A 



