1 56 Campbell . — On the Development of 
examination will show caroliniazia to occur in California, 
remains to be seen, but its occurrence must at present be 
regarded as doubtful. 
A. jiliczdoides is common in many parts of California, and 
often occurs in great quantity, so that the surface of a pond, 
or a quiet stretch of river, may be completely hidden. As 
the leaves are strongly tinged with purplish red, the plants 
are then very conspicuous and recognizable from some 
distance away. 
Observations were begun in November, 1891, and continued, 
except during the summer, until October, 1892. Most of the 
material was taken from a pond about a dozen miles from 
Palo Alto, but specimens were also received from various 
points south. For some reason the plant disappeared com- 
pletely from the pond mentioned during the past summer, 
and in September no trace of it was to be found except 
the fragments of the dead plants. As the plants were 
abundant and vigorous the year before at about the same 
time, it seems hardly likely that this is always the case. 
Ripe spores that germinated promptly were obtained from 
the decaying fragments of the plants, and probably will serve 
to stock the pond again, as the plants spread with great 
rapidity when once established. 
Our knowledge of Azolla is based mainly upon the papers 
of Strasburger 1 and Berggren 2 . Several earlier writers, 
Griffith, Mettenius, Meyen, and Martius, are referred to by 
Strasburger, but their works were not accessible. The results 
of their observations, however, are given by Strasburger in 
his admirable monograph of the genus. 
Strasburger’s work deals very exhaustively with the anatomy 
and histology of the mature sporophyte, and also of the full- 
grown sporangium and spores. The development of the latter 
he was not able to follow for lack of material. Berggren's 
paper deals with the female prothallium and embryo, and 
while valuable as the only contribution to our knowledge of 
1 loc. cit. 
2 Om Azollas prothallium och embryo. (Lund’s Univ. Arsskrift. t. xvi.) 
