62 BOTANICAL GAZETTE [JANUARY 
Following Lrerrcres (6), he further separates the Marchantioideae 
into the Astroporeae, Operculatae, and Compositae. CAvERs (2) 
has shown that the characters which separate these groups are 
not entirely constant; yet he recognizes their individuality, but 
elevates them to the rank of families and renames them Cleveaceae, 
Aytoniaceae, and Marchantiaceae. Reboulia belongs to the 
Operculatae of LEITGEB or to the Aytoniaceae of CAVERS. 
Material 
The writer is indebted to Dr. W. J. G. Lanp for the material 
used in this investigation. Four collections were made by him 
over a period of ro years during the months of September, October, 
and November at Rome, Indiana. A few of the slides were made 
by Mr. S. A. Ives, but most of them were prepared by the writer. 
Thallus 
The gametophyte plant body of Reboulia hemisphaerica is a 
pale green, dichotomously branched thallus with slightly undulate 
margins and a distinct midrib. Rhizoids and scales arise from 
the ventral surface. Both smooth and pegged rhizoids occur, 
their ends often being highly contorted when in contact with soil 
particles. The dark red ventral scales are 2-ranked and point 
diagonally forward and outward. They do not arise from the 
splitting of a single scale as in most species of Riccia, but are 
separate from the beginning. The scales are 1 cell thick except 
near their place of attachment to the thallus where they are often 
2 cells thick. They are unappendaged. 
The body of the thallus is differentiated into a lower colorless 
region of compact elongated cells with rather thick walls, and an 
upper region of loose chlorophyllose tissue containing large air 
chambers. Intracellular fungi live in the lower region (fig. 5)- 
The walls of the epidermal cells are slightly thickened and are 
devoid of chloroplasts except near the growing point of the thallus 
(fig. 2). The plastids in the air chamber region are rather large 
and contain several starch grains with distinct hila. Plastids in 
the cells in the growing region are small and contain no starch. 
The development of the large starch-producing plastids was 
