174 BOTANICAL GAZETTE [MARCH 
young sporophytes, completely destroying them and filling the 
venter of the archegonium with a dense mass of the smut spores. 
These spores are so much smaller and so much more numerous 
than the Ricciocarpus spores that the infected sporophytes are 
recognized at a glance. Although the fungus enters the arche- 
gonium soon after fertilization, the young sporophyte continues 
to grow, apparently following the normal course of develop- 
ment up to the spore mother-cell stage, and even to the forma- 
tion of spores. By this time, however, the mycelium and 
numerous spores of the fungus are tightly packed about the Ric- 
ciocarpus spores, which soon break down and are destroyed by 
the encroaching fungus (fig. 4o.) 
The life history of the fungi inhabiting various liverworts was 
carefully followed by Cavers (10). He states that the fungal 
hyphae usually grow down the neck of the fertilized archego- 
nium, but they may pierce the venter and thus enter the sporo- 
gonium directly. In all cases where the sporogonium is invaded 
the relation of host plant and fungus is regarded as pure para 
sitism. Where the fungus penetrates only gametophyte tissue it 
may form a mycorhiza, the host plant living as a saprophyte, the 
relation of fungus and host being apparently that of symbiosis. 
I am under obligations to Professor J. M. Coulter and Dr. C. 
J. Chamberlain for suggestions and advice during this study. 
SUMMARY. 
1. When fruiting, Ricciocarpus is essentially a free floating 
plant. 
2. The genus is strictly monoecious, though a small number 
of plants fail to produce archegonia. 
3. Sex organs are produced in single definite groups a 
Asterella, etc. Antheridia are produced on very young plants, 
which later produce archegonia and sporophytes. 
4. The basal cell of the archegonium develops a structure 
which is partially imbedded in the storage tissue and acts as the 
physiological equivalent of the sporophyte foot in higher fore 
5. There is no rudimentary integument of the archegonium. 
6. The diameter of the male nucleus is about one-half that of 
the female nucleus. 
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