— 72 — 
OXYMITRA (TESSELLINA) IN THE UNITED STATES 
Marshall A. Howe 
The family Ricciaceae, as treated by Schiffner in Engler & Prantl, Die 
natiirlichen Pflanzenfamilien , 1 comprises three genera, Riccia, Ricciocarpus, and 
Tessellina. Alexander Braun’s genus Ricciella, with Riccia fluitans L. as the 
type, has been accepted as valid *by Warnstorf , 2 by Evans , 3 and by some other 
writers on the Hepaticae, though Schiffner, K. M idler , 4 and perhaps the ma- 
jority of the modern 
students of the He- 
paticae prefer to con- 
sider it a subgenus of 
Riccia. Occasionally 
a recent student 5 has 
doubted the validity 
of the genus Riccio- 
carpus, but no one in 
recent years, so far as 
I am aware, has had 
any scruples in recog- 
nizing the generic 
rank of the remark- 
able plant currently 
known as Tessellina. 
The groups known as 
Riccia , Ricciella , and 
Ricciocarpus , whether 
genera or not, have 
long been recognized 
as having North Am- 
erican represent- 
atives, but the genus 
Tessellina , with its 
single species, was 
known only from the 
Mediterranean region of Europe and Africa until Balansa, somewhat more than 
thirty years ago, found it in Paraguay. Stephani 6 has reported it from Brazil 
Fig. i . — Oxymitra paleacea Bisch. Nat. size. Sterile. Grown 
at the N. Y. Botanical Garden from specimens collected 
near Austin, Texas, by Dr. M. S. Young, Feb. 1914. 
1 l 3 : 8-15. 1893. Schiffner spells Tessellina with one “ 1 ”, though Dumortier, the author 
of the name, seems consistently and correctly to haye used two “1/s.” 
2 Kryptogamenflora der Mark Brandenburg 1 : '80. 1903. 
3 Rhodora 9 : 56. 1907. 
4 In Rabenhorst, Kryptogamen-flora von Deutschland, Oesterreich und der Schweiz 6: 140. 
141- 1907. 
5 See Lewis, C. E. The embryology and development of Riccia lutescens and Riccia crystal- 
lina. Bot. Gaz. 41 : 109-138. pi. 5-9. 1906. 
6 Bull. Herb. Boiss. 6: 759. 1898. 
