No. 387.] PLANT MORPHOLOGY AND PHYSIOLOGY. 205 
tubers has long been known to systematists. This number has been 
recently increased until, at the present time, at least eleven species 
are known in which tuber-like growths occur. Of these, four belong 
to the genus Anthoceros, three to Riccia, two to Petalophyllum, one 
to Fossombronia, and one to Geothallus. It is to be expected that as 
the hepatic flora of the drier regions of the earth comes under more 
extended and accurate investigation, this evident adaptation for 
carrying the plant over a season of drought will be found to be much 
more common than has been generally supposed. 
In the Californian Anthoceros phymatodes the tuber appears as a 
swelling near the apparent apex of the more or less well-defined costa 
of a Thallus-segment, becoming soon strictly ventral through the 
continued onward growth of the segment, and coming at the same 
time to be pendant from the ventral surface through the formation of 
a fleshy or slender and elongated peduncle. Tubers are globose 
or ellipsoidal in form, 0.25 to 1 mm. in diameter, at first smooth, but 
becoming at length thickly covered with root hairs. A cross-section 
of the body of the tuber shows it to consist of a cortex of 2 to 4 
layers of nearly empty cells enclosing a central mass of smaller cells 
so densely filled with oil drops or with merely colorless granules that 
the cell boundaries in a section are rendered obscure. There is very 
little if any starch. In two cases, old tubers of Anthoceros phymatodes 
were found sending out new shoots, demonstrating that they play a 
part in the vegetative propagation of the plant. What had simply 
been inferred in regard to the function of these organs in the three 
tuber-bearing species of Anthoceros previously known has now been 
observed in this Californian species. 
Dr. Henry KRAEMER: Morphology of the Genus Viola. — About 
30 species of violets, chiefly from the United States, have been ex- 
amined with special reference to style and stigma, stamen spur, size 
and shape of the pollen grains, hairs upon the stamens and petals, 
presence of bracts, mucilage cells, etc. The paper, which represents 
a large amount of painstaking work, was illustrated by many drawings, 
photographs, and photomicrographs. 
Bracts with characteristic mucilage-secreting hairs occur in all of 
the species, and sub-epidermal mucilage cells are present in the leaf, 
stem, and all parts of the flower except the stamens. 
A number of species agree in having a nearly globular stigma with 
a more or less well developed lip-like appendage, a style with a genic- 
ulate bend in the lower part, and corkscrew-shaped hairs on the 
