SOME NOTES ON AZOLLA. 
BY DOUGLAS HOUGHTON CAMPBELL. 
One of the most interesting of the native Pteridophytes of Califor- 
nia is the widel¥ distributed Azolla filiculoides,occasionally called 
‘‘water-fern.’’ This pretty little plant is common in many localities, 
and when found at all, usually occurs in great numbers, and often 
covers extensive stretches of quiet water with a dense purple-red 
mantle so thick that the water is completely hidden. Sometimes, 
however, a pond that is completely covered with the plant, may, after 
a few months, show no trace of it beyond a few decaying fragments 
that have sunk to the bottom, or are entangled among the Lemna 
and other floating weeds on the surface. Whether this sudden dis- 
appearance is due simply to the plant’s having completed its natural 
term of existence, or to some other cause, I am unable to say. A 
pond near the La Honda road, some dozen miles back of Palo Alto, © 
was visited repeatedly between November 1891 and May 1892, and 
at all times was covered with a luxuriant growth of Azolla. The same 
pond visited in September, showed not a single living plant, although 
ripe spores were found in the decaying masses of plants at the bot- 
tom of the pond, and these germinated promptly when set free and 
placed in clear water. The pond has not been visited since, so I 
cannot say whether or not a new generation of plants has appeared. 
The genus Azolla is a small one, but widely distributed. Of the 
four species usually recognized, tw are American, viz.: A. flicu- 
loides and A. Caroliniana; A. nilotica is African, and A. pinnata is 
Asiatic and Australasian. Both A. A/iculoides and A. Caroliniana are 
attributed to California, but all specimens yet seen by me have be-. 
longed to the former species, and as these included some from the 
collection of the Academy of Sciences labeled 4. Caroliniana, I have 
some doubts about this species occurring here. This is the species 
of the eastern part of the continent, where it is widely distributed 
and reaches as far south as Brazil. 4. filiculotdes occurs in Chile 
and Peru, and probably pretty much all along the Pacific Coast. 
As the life history of all the species was very imperfectly known, 
an effort was made to clear up as far as possible the obscure points. 
To this end observations were begun in November, 1891, and con- 
tinued, with more or less interruption, for a year. Only a few of 
the more important and general points brought~out by these investi- 
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