Contributions to the histology of the Pontederiacex. 
EDGAR W. OLIVE. 
WITH PLATE XVII, 
Comparatively little work has been done on the histology 
of the Pontederiaceez. The roots have been studied some- 
what ina comparative way by M. Treub, L. Morot, F. Hilde- 
brand, S. Schénland, and others. A comprehensive study of 
the anatomy of water-plants was begun by F. Parlatore, but 
death prevented the completion of the work. Nine plates, 
however, were published in 1881. These contain among the 
drawings of about ninety species of water-plants a few very 
diagrammatic drawings of two species of Pontederia. No ex 
planation accompanies the plates. : ‘ 
Solms-Laubach has a monograph of the Pontederiacee 
A. et C. de Candolle’s Monographie Phanerogamarum, but a 
short review of this’ shows that it is systematic rather than 
histological. J. Duval Jouve, in 1873, investigated the dia- 
phragms, or cross-plates, in the air-cavities of Pontederia 
cordata. E. M. Wilcox, in the Yournal of the Cincinnati ai 
of Nat. Hist., July—Oct., 1893, has noted a few points ne 
histology of the same species. 4 
In the botanical laboratories of Wabash College, a 
studies were made in the spring of 1893 upon the histo i 
of Pontederia crassipes, a cultivated form, and since thena © 
parative study of all the available members 
undertaken and types of other aquatic plants ex 
Pontederiacee are aquatic herbs, growing in mud, ¢ 
water. There’ are two genera embracing four spec! f which 
northern United States flora, all but one species of Ww 
(Heteranthera limosa) are reported in our Indiana pecs 
the four species have been studied, as well as the cu en 
Pontederia. In the world’s flora there are reported 7 rin- 
three species and six genera? grouped under this order, P 
cipally tropical in their habitat. : : i 
Pontederia crassipes Mart. (see fig. 1) is an interes 
*Botanischer Jahresbericht 11: 622. 1883. 
*Bot. Gaz., 6: Supplement. 1881. 
*MacMillan, Metaspermz of Minn. Valley. 1892. 
or vessel Of 
cultivated aquatic, growing rapidly in a basin | : 
