ON THE HABITS OF SPECIES OF LEMN2. 323 
On the Habits of Lemna minor, L. gibba, and L. polyrrhiza. By 
H. B. Guppy, M.B. (Communicated by W. Borrine 
Hemstey, F.R.S., A.L.S.) 
[Read 3rd May, 1894.] 
AFTER three years’ systematic observations of these plants *, I 
find that in this branch of the subject my notes add but little to 
what Hegelmaier recorded about a quarter of a century ago in 
his general work on the Lemnacew. Though that work is con- 
cerned chiefly with their structural characters, it cannot easily 
be supplemented now without a great amount of observation and 
experiment based on new lines of research. 
These plants at first sight seem well fitted for an inquiry into 
their adaptation to the conditions of their existence; and 
Professor Miall, in an interesting lecture at the Royal Insti- 
tution in March, 1892, treated of some of their relations to the 
physical characters of water. Eminently suited as the duck- 
weeds are for aquatic life, it is a little perplexing that they will 
thrive just as well on wet mud. 
For twenty months I have cultivated Lemna minor on wet 
mud, where it throve and budded all the seasons of the year. To 
give an instance, two plants set apart in October had increased 
to twenty by April, and to fifty by the next October. Nor has 
this long exposure to different habits of life produced any per- 
manent change in the characters of the plants so far as their 
external appearance is concerned. After a culture of twenty 
months on the mud the plants still float on water and retain 
their root-caps, even in cases where the roots have penetrated a 
line or two into the soft mud. The winter fronds of Lemna 
polyrrhiza, also, wheu placed on wet mud in the spring, bud 
freely, and in the course of a few weeks produce the summer form 
of the plant. Duckweed stranded on the mud during the drought 
of the summer of 1893 remained alive most of the season 
wherever the earth around the ditch or pond remained moist. 
Lemna minor is to be observed flourishing on the wet soil and oozy 
ground in the vicinity of springs some feet above the level of the 
pool beneath; and here it can safely withstand the longest 
* In the South-east of England, in Epping Forest and around Kingston, and 
in the rivers Thames and Lea. 
