200 Transactions. 



longitudinal section the elongated cells of the palisade layer are seen to be 

 from four to six deep. They overlap one another, and, contrary to what 

 Lang has described in L. davatum, they show the presence of dense fungal 

 coils in all the cells, as well as the mycelium which inhabits either the cell- 

 wall itself or the spaces between the cells. At its interior boundary the cells 

 of the palisade layer are shorter in form, and where they abut on to the 

 upper region of empty parenchyma cells the cells of the latter tissue are 

 n^uch flattened in form. Miss Edgerley, in her account of this prothallus. 

 (12, p. 96) says that '' the whole of the central part of the prothallium i;^ 

 occupied by large thin-walled parenchyn>atous storage cells, in which starch 

 is stored in great abundance. The cells of this tissue bordering on the 

 palisade layer are often smaller and more densely filled with starch- 

 granules." I found no starch in any of the older or the young prothalli 

 which I sectioned. Possibly this difference is to be accounted for by a 

 difference in the season of the year in which Miss Edgerley's and my own 

 prothalli were collected. The upper fungus-free region of the prothallus, 

 which bears the sexual organs, is in full-grown specimens very irregularly 

 developed into large rounded protuberances, which overlap the original 

 saucer-shaped upper surface. The fungal zones extend inip such of these 

 protuberances as lie towards the rim of the upper surface. In such cases 

 as these in some longitudinal tangential sections the prothallial epidermis 

 and the cortical fungal zone extend almost entirely around the section, 

 the whcde of the interior being occupied by palisade tissue, while a very 

 small upper corner of the section consists of the upper noir-fungal tissue. 

 The youngest prothalli sectioned consisted almost entirely of fungal tissues, 

 more especially of the palisade layer, with a very feeble development of the 

 upper non-fungal zone. There is no store tissue containing starch either 

 in the young or mature prothalli such as Bruchmann figures in L. davatum — 

 in fact, the only starch which I found present consisted of a few scattered 

 grains is some of the palisade cells. One very large prothallus, which grevs" 

 at the surface of the ground, and whose upper region was vivid green in 

 colour, showed a considerable divergence from the normal structure of the 

 prothallus as just described. The palisade layer was four to five cells 

 in thickness, but by far the major bulk of the prothallus consisted of the 

 upper non-fungus-containing parenchyma. Moreover, this contained a large 

 accumulation of starch both in the layer immediately underlying the small- 

 celled, generative region and also around the meristem. The starch was 

 also thickly accumulated around the " foot '" of a developing plantlet. In 

 the palisade cells there was an abundant accumulation of oil-globules and 

 starch, and the epithelial cells of the '' foot " of the young plant were densely 

 crowded with contents. I have several times come across these green, 

 surface-growing prothalli. 



The nature of the fungal zones in the prothallus of L. fastigiatum is 

 identical with that of L. voluhile. The most striking feature in it is the 

 enormous development of the palisade layer. In some of the largest pro- 

 thalli sectioned lobing of the upper surface had taken place and the fungal 

 zones had extended into these lobes, giving to the sections a very irregular 

 ajjpearance. Also, in the large prothalli the Up sometimes greatly grows 

 over inwards, with the result that the fungal zones become somewhat 

 superimposed upon one another, as has been described above in L. volvbile. 

 The youngest prothalli found by me were of two forms. The first were of 

 the usual saucer shape, showing the first-formed conical projection on the 

 lower surface. Those of the second form were dichotomouslv forked, as I 



