MORPHOLOGY OF THE LEMNA FROND 
FREDERICK H. BLODGETT 
(WITH PLATE XIV AND ONE FIGURE) 
In the case of structures simplified by reduction, it is sometimes 
necessary to trace the development of the parts through their imma- 
ture stages in order to understand the morphology of the mature 
individuals. This has especial interest when the normal method 
of reproduction depends upon the development in rapid succession 
of vegetative propagules, as in the Lemnaceae. The character of 
such greatly reduced bodies has been variously interpreted, being 
regarded as stem, leaf, or both fused together, by different writers; 
while some use a term like ‘‘disklike bodies.”” Since GRAy’ used 
Lemna as the type of ‘‘frondose stem or frond,” this name will be 
used for convenience through the paper. In but few of the articles 
mentioning the character of the frond has any attempt been made 
to indicate the basis for the choice of terms, even HeGELMAIER? 
depending largely upon academic argument rather than upon 
structural details in his discussion of the frond. CALDWELL‘ 
devoted most of his attention to the development of the flower 
parts, and did not attempt more than a review of the general char- 
acter of the frond as presented by others. In the following notes 
an effort is made to show what structural units contribute to the 
formation of the frond and the part taken by each in the develop- 
ment of the successive vegetative individuals. 
Inception of frond rudiment 
The Lemna frond is characterized by a sheath or pouch on each 
side of the base. Within each of these pouches a frond of the next 
vegetative generation arises, but the two do not develop at the 
same time. When flowers are produced each one grows in the 
« Gray, Asa, Structural botany. New York. 1879 (p. 67). 
2 HEGELMAIER, F., Die Lemnaceen. Leipzig. 1868. 
3 CALDWELL, Or1s W., Life history of Lemna minor. Bot. Gaz. 27: 37-66, 1899. 
383] {Botanical Gazette, vol. 60 
