Black — The Morphology of Ricci a Frostii, A test. 515 
it a primitive form of epidermis. The upright filaments and the tissue 
beneath contain chlorophyll. The air-chambers in Riccia Frostii , Aust., are 
open their entire width, i.e. they are not overgrown by the surface develop- 
ment of the epidermis. An examination of Ricciocarpns natans 1 and other 
Marchantiales ( Marchantia polymorpha , Fegatella conic a, and Asterella) 
showed the origin of the air-spaces to be similar to that described by Barnes 
and Land. If the splitting occurs within the thallus in Riccia Frostii , Aust., 
it would seem reasonable to find stages that have not yet reached the 
surface, such as are found with no difficulty in Ricciocarpets natans and other 
forms. But in all the material examined the cell relations are unmistakably 
clear, and no stage was found with an internal space not yet broken out to 
the surface. 
As before stated, the thallus of Riccia Frostii , Aust., is strictly 
dioecious. The sexual organs are scattered irregularly in acropetal succession 
in the thallus. Goebel (1. c., p. 80) speaks of the disposition of the sexual 
organs in Riccia as diffuse, and considers it a primitive type. 
Development of the Sexual Organs. 
Although several hundred slides were made of as many plants of Riccia 
Frostii , no sterile plants were found. No thallus was found, young or old, 
bearing both antheridia and archegonia. The sexual organs are produced 
continuously as long as the thallus lives. There is thus no definite fruiting 
period. 
The development of the archegonia and antheridia conforms to the 
hepatic type, and has been fully described by other writers. The antheridium 
initial is distinguished by its dense contents from the adjacent cells before 
it projects above the surface of the thallus. The initial cell in Riccia 
Frostii divides transversely before it has projected much above the other 
cells. The antheridium scarcely projects above the surface of the thallus, 
for, as it elongates, the tissue immediately surrounding the antheridium 
develops, sometimes level with it (Fig. 10), sometimes a little lower than it 
(Fig. 9 a), and eventually surpasses it (Figs, gb and 11), leaving the 
antheridium an embedded or sunken structure. The antheridial wall is cut 
off early (Figs. 12 and 13). The end cells of the filaments adjacent to the 
antheridium are distinguished from the first by dense contents (Figs. 9 b and 
11). These cells form the canal, or opening, leading to the antheridium, 
through which the sperms are discharged (Fig. 13). Cell-division in the 
antheridium soon overtakes cell growth, and many cells eventually occupy 
the place of a few. As the antheridium matures, the cells of one group 
divide simultaneously. Usually several groups of cells are active, so that 
in one antheridium many stages of division may be found. The cells are 
1 Slides belonging to Mr. Fermen L. Pickett. 
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