488 MOSSES AND FERNS chap. 



right cylindrical body, seldom, apparently, exceeding about 

 two mm. in height. The base is more or less completely 

 buried in the ground, and contains but little chlorophyll. The 

 summit is surrounded by the lobes already spoken of, and these 

 have somewhat the appearance of leaves crowning a short stem. 

 The whole structure of the prothallium recalls in some respects 

 that of Eqiiisctum, but differs in the important particular that 

 it is radially constructed, and is not dorsi-ventral. 



Besides the type of prothallium found in L. ccrnmun, with 

 which L. iniindatum closely agrees, Treub has also studied the 

 very different prothallium of L. phlcgmaria, and others of sim- 

 ilar habit. Tliese are only known in their mature condition, in 

 which they are saprophytes, growing in the outer decayed lay- 

 ers of bark upon the trunks of trees. In this condition they 

 are extremely slender branched structures, totally different 

 from those of L. cermnun, both in form and in the complete 

 absence of chlorophyll. Like the prothallia of many Hymeno- 

 phyllacese, they multiply by special gemmae and apparently may 

 live for a long time. Like those of L. cermmm they are always 

 infected by an endophytic fungus. 



Bruchmann (4) finds that there is a good deal of differ- 

 ence among the European species. L. clavatiim (Fig. 284, A) 

 and L. annotinum represent one type. The gametophyte is 

 subterranean, and in appearance not very different from that 

 of Botrychhim, although its manner of growth is of an entirely 

 different type. In the earliest stages observed, it was an up- 

 right, top-shaped body, the upper surface of which was some- 

 what depressed below the margin, which forms an elevated rim 

 about the central area. There is no proper apical growth, but 

 a zone of cells between the rim and the central area is meriste- 

 matic, and to the growth of this zone the future development of 

 the gametophyte is due. The whole of the central area is de- 

 voted to the formation of the reproductive organs, and consti- 

 tutes the "generative tissue," and like the similar tissue in Bo- 

 trychium, its cells are almost destitute of granular contents. 

 Outside the colourless generative tissue is a layer of dense stor- 

 age-cells, and outside of these a layer of tissue in which is an 

 endophytic fungus. Unicellular rhizoids occur iii consider- 

 able numbers upon the under surface. 



The gametophyte of L. complanatum (Fig. 284, C) is also 

 subterranean, but quite dift'erent in form from that of L. clav- 



