V THE ANTHOCEROTE.C 117 



The type of the order, AntJioceros^ includes fifteen to twenty- 

 species distributed over the world, but especially luxuriant in 

 the tropics. The species that has been most studied is the 

 cosmopolitan A. IcBvis, which has been the subject of repeated 

 investigations by numerous botanists. This species was carefully 

 examined by the writer, as well as the larger A. fusiforviis, 

 a common Californian species allied to A. piinctaUis. The 

 gametophyte is a fleshy dark -green or sometimes yellowish 

 green thallus, which branches dichotomously, so that it often 

 forms orbicular discs like those of the Marchantiaceae, but owing 

 to the very rapid division of the growing points, and the irregular 

 form of the margin, the individual apices are not usually 

 recognisable. The thallus is either smooth, as in A. IcEvis, or it 

 is very much crisped and roughened by ridges and spines upon 

 the upper surface. On cutting into the plant great quantities 

 of colourless mucilage escape. Here and there, scattered through 

 it, are dark blue-green specks, the Nostoc colonies always 

 found in the thallus. Colourless root -hairs fasten it to the 

 ground. No indications of the sexual organs can be seen from 

 the outside, and it is sometimes difficult to procure them for 

 study, as in both species their formation ceases very soon after 

 the sporogonia begin to develop, and when these are large 

 enough to be seen with the naked eye it is too late to procure 

 the young sexual organs. 



The sporogonia are produced in great numbers, especially 

 in A. fiisifonnis (Fig. 55, A), where they reach a length 

 of 5 to 6 centimetres, or even more, and stand so closely 

 together that a patch of fruiting plants has the appearance 

 of a tuft of fine grass. In California the plants are annual. 

 The spores germinate in the autumn with the commence- 

 ment of the winter rains, and the sexual organs are mature 

 by about the middle of January. As soon as fertilisation 

 is effected the development of sexual organs ceases, and the 

 regular apical growth stops, the margin of the thallus growing 

 out irregularly beyond the young sporogonia, which are thus 

 left some distance from the margin. After they are once formed 

 they grow as long as the thallus remains alive, and this, in 

 California, usually continues until about the ist of May, when 

 with the cessation of rain the thallus gradually dries up. I saw 

 no evidences of the thallus surviving the dry season, as is the 

 case with Riccia and Targionia. 



