36 



it a subgenus of Melobesia, but the latter is probably to be re- 

 garded a rather well defined genus, to which Lithophyllum is less 

 related than to Lithothamnion. 1 ) 



I have divided Eulithothamnion into two sections, Innatæ 

 and Evanidæ, the one comprising species by which the concept- 

 acles of sporangia grow down into the frond, the other species 

 by which this is not the case. There is, certainly, not any de- 

 fined limit between these two sections, as transitions now and 

 then are to be found, but that appears rather to be conditioned 

 by external causes. Sometimes in species of the first named sec- 

 tion, by which the thickening meristema of the frond apparently 

 is superficiai, overlapping the roofs of the conceptacles and the 

 latter growing down into the frond the cavity may be found filled 

 with new-formed tissue. That is, however, so far as I have seen, 

 nearly always formed by new local formations and most often in 

 species by which the conceptacles are not much immersed, and 

 the whole roof for some reason fallen away, or dissolved. Toge 

 ther with the overgrown conceptacles is to be found some sporan- 

 gium not escaped, or sometimes even all or nearly all the sporangia 

 formed, partly apparently mature partly but little developed. In 

 species of the other section, with the thickening meristema of the 

 frond apparently lying below the basal surface of the conceptacles, 

 I have never seen overgrown ones, not even in species with im- 

 mersed conceptacles. 



The conceptacles of cystocarps and antheridia always use to 

 be superficiai, or as a rule very little immersed. The former ge- 

 nerally do not grow down into the frond, the whole roof falling 

 away and leaves a cup-shaped scar in most cases with elevated 

 edges. The latter, probably, do not, as a rule, become overgrown. 

 I have in four species of the section Innatæ (L. deliiscens, L. 

 fruticulosum, . L. polymorphum and L. flavescens) seen overgrown 

 conceptacles of cystocarps. This is caused thereby, that the roof 



*) „\Venn schon zwischen Melobesia und IAihophyllum intime Beziehungen 

 bestehen, so lassen sich diese Gattungen doch im entwickelten Zustand 

 wenigstens an bestimmten Merkmalen erkennen". Solms-Laubach 1. c 

 p. 26. 



