Biology of Fegatella conic a. 91 
localized in the pointed cells, and that the solution absorbed by the 
rhizoids had passed through the ventral tissue of the thallus into the green 
filaments, and had become concentrated in the terminal cells owing to 
continued evaporation. 
Ventral Tissue. 
The compact tissue underlying the air-chambers is well developed 
in the midrib, but in the lamina on either side is much thinner, becoming 
reduced to two or three layers of cells near the margin of the thallus 
(Plate VI, Fig. 18). This tissue consists chiefly of large colourless cells, 
containing starch-grains and having their walls thickened by anastomosing 
fibres, the unthickened portions remaining as slit-like pits (Plate VI, Fig. 
21). Towards the lower surface of the midrib the cells are much smaller 
(excepting the large cells which grow out to form rhizoids), and have 
thick dark-coloured walls forming a kind of ventral cortex. 
The cells of this compact tissue sometimes contain coiled chains 
of Nostoc ; colonies of this Alga are frequently observed in the groove 
enclosed by the ventral scales and amongst the rhizoids (Plate VI, Fig. 20). 
Endophytic (perhaps symbiotic) blue-green Algae have long been known 
to inhabit specialized organs in Blasia and the Anthoceroteae, but 
apparently their occurrence in the tissues of the Marchantiales has only 
been recorded hitherto by Reinsch (1877, p. 234), for a Riccia, , and by 
Mattirolo (1888, p. 7), for Grimaldia dichotoma . Nostoc- colonies have 
been observed by the writer in the compact tissue of the thallus of Reboulia 
hemispherical Preissia commutata , and Targionia hypophylla , and it is 
probable that they are of general occurrence in the thalloid Hepaticae. 
We may here describe two tissue-elements which are especially well 
developed in Fegatellai and which occur chiefly in the compact ventral 
tissue, viz. (1) oil-bodies, (2) mucilage-sacs. 
The oil-bodies are spherical or ovoid in form, dark brown in colour, 
and from 20 {jl to 40 /x in diameter. They occur singly in special cells, 
each of which is nearly filled by the oil-body (Plate VI, Fig. 21, O. c.). 
Similar bodies occur in many other liverworts, and they were first carefully 
studied by Pfefifer (1874), who found that they contain water, a proteid 
substance, oil, and in some cases tannic acid, these constituents being 
mixed and forming an emulsion, held together by an envelope consisting 
of proteid matter. Previous to the appearance of Pfeffer’s memoir the 
oil-bodies of the Marchantiaceae had been noticed and described by 
various observers. Mirbel, in his classical work on Marchantia polymorpha 
^ 835)3 first described them, and believed that they consisted of starch. 
Gottsche (1842, p. 287), showed that these bodies do not give the reaction 
of starch ; he found that on treatment with alcohol the contents were 
dissolved and a sac-like membrane remained behind, and concluded that 
