American Species of Marchantia. 211 



nature. He showed that they occurred not only under the 

 epidermis, as he expressed it, but also in the compact ventral 

 tissue and in the partitions between the air-chambers, and he 

 emphasized the fact that they were especially abundant in the 

 female receptacles. The distribution of the slime-cells in Mar- 

 chantia was a little later discussed at length by Prescher.^^ He 

 found no trace of them in M. Berteroana, M. papillata, M. emar- 

 ginata R. Bl. & N., or M. linearis; he found them restricted to 

 the compact tissue of certain definite regions in M. polymorpha 

 and M. paleacea; and it was only in M. chenopoda (including 

 M. cartilaginea) that he found them in the epidermis. 



Surface papillae have been figured very accurately by Kny 

 in the case of M. polymorpha. They are minute appendages 

 of the epidermis, which are cut off by walls and rounded or 

 bluntly pointed at their free ends (Fig. 2, J, L, O, P). Sometimes 

 a papilla is situated over a single cell and sometimes over the 

 partition between two cells, showing in the latter case that an 

 epidermal cell had divided after the papilla had been formed. 

 Papillae of this type seem to be rare on vegetative branches and 

 confined to certain species. So far they have been reported m 

 two East Indian species, M. emarginata and M. Treubli Schirfn., 

 but they seem to be absent from all the American species except 

 M. polymorpha. In this last species, as shown by Schiffner,^* 

 the median portion of the thallus is always free from papillae, 

 while the marginal regions sometimes show them clearly. The 

 distribution is very different, however, in M. Trenhii, where the 

 papillae are most abundant in the median portion and gradually 

 decrease toward the margins. Whether papillae of this character 

 form a constant feature of any of the species where they have 

 been found is perhaps doubtful. In one specimen of M. emar- 

 ginata, for example, in the writer's collection (Schiffner, Iter 

 Indicum 57), the plants seem to have developed no papillae, and 

 they are frequently absent from the vegetative branches in M. 

 polymorpha. When they occur on receptacles or cupules, as in 

 this same species, they seem to be more constant. 



" Die Schleimorgane der Marchantieen. Sitzungsb. Kais. Acad. Wissen. 

 Wien, Math.-naturw. CI. 86' : 132-158. pi. i, 2. 1882. 

 "^Bot. Wandtafeln pi. 84, f. 2, 3. 1890. 

 " See Schififner, FI. de Buitenzorg 4: 32, 35. I.eiden, 1900. 

 " Lotos 49 : 93. 1901. 



