74 Hirsu : AIR CHAMBERS IN THE RICCIACEAE 
of Ricciocarpus natans, which was obtained from the marshes near 
the southern end of Cayuga Lake. In addition, material of Riccia 
Frostii Aust., which had been preserved in alcohol, was used.* 
For comparative purposes herbarium material of Riccia nigrella, 
R. glauca, R. Miyakeana, R. crystallina, R. arvensis hirta, R. 
fluitans, R. Donnellii, and Ricciocarpus natans was studied. This 
was prepared for sectioning by first soaking it in dilute KOH and 
warm water before running it through the alcohols and cedar oil, 
and imbedding finally in paraffin. Although the tissue of this 
herbarium material was distorted and could not be used as a basis 
for positive statements or drawings, it was evident that the first 
three species named presented a different type of air chamber from 
that found in the two species studied by Barnes and Land; and 
the earliest stages suggested an entirely different origin. Azecia 
Frostit Aust. also exhibited the same type of air chamber ; and as 
this had been preserved in alcohol the tissue was in good condi- 
tion, so that satisfactory sections through the apical region could 
be obtained and the development of the air chambers could be 
followed with certainty. 
A study of Ricciocarpus natans showed that in every instance 
the air spaces arise through cleavage. The figures (1-3 inclusive), 
IGURE Ricciocarpus natans. Verti- FIGURE 2. Ricciocarpus natans. 
cal longitudinal section of thallus near the Section nearly parallel to the surface 
growing point. 4, early stage of an air cham- showing origin of air chambers. 
ber; 8 and C, older chambers which have 
opened to the outside. 
made from sections close to the growing point, display this clearly. 
There is no doubt concerning the origin of space A in FIGURE I. 
B and C in the same figure show older spaces that have opened 
out to the surface Ficure 3, A, indicates cell division preparatory 
* The material was collected near the ‘*Kaw River,’’ Kansas, by an unknown 
collector, ‘The writer is indebted to Professor Alexander W. Evans for its determination- 
+ 
