On the Life-history of Salvinia natans . 1 
BY 
KONO YASUI, 
Assistant Professor of Botany in the Higher Normal School for Women, Tokyo. 
With Plates XLI-XLIIX and one Figure in the Text. 
ALTHOUGH the germination of the micro- and macrospore and the 
J~\_ embryo-formation of Salvinia natans had already been observed by 
several of the older investigators, such as Mettenius (’46), Hofmeister (’51, 
57), and others, the first careful and complete account of the subject was 
given by Pringsheim in 1863. In his classical paper he followed pretty 
closely the development of the male and female gametophytes, and the 
formation of the embryo, besides describing very carefully the further 
development of the sporophyte. Pringsheim’s paper may, therefore, be 
looked upon as the starting-point upon which all subsequent morphological 
studies on Salvinia natans are based. 
In 1873 Juranyi published the results of his studies on the develop- 
ment of the micro- and macrosporangia and the formation of spores. 
These parts of the life-history of Salvinia natans were entirely neglected 
by Pringsheim, and Juranyi’s paper may be considered as the first care- 
ful description of this subject. Three years later Arcangeli (76) described 
the development of both sporangia and prothallia of Salvinia. He noticed 
the three layers, i. e. the pseudo-epispore, the exospore, and the endospore, 
in the spore-coat of both the macro- and microspore. The pseudo-epispore 
of the latter is considered by him to be common to all microspores. He 
also noticed that there are two antheridia in one male prothallium. 
In 1879 Prantl’s short paper appeared, dealing chiefly with the develop- 
ment of the female prothallium of Salvinia. He clearly demonstrated the 
existence of three spore-coats in the macrospore. In the same year Bauke 
(79) described the further behaviour of the unfertilized prothallia of Sal- 
vinia. He confirmed and extended the statements of Pringsheim. A few 
years later Heinricher (’82) studied the development of the macro- and 
microspores, and corrected and extended the results of Juranyi. 
1 The substance of this paper has been already published in Japanese in the Botanical Magazine, 
Tokyo, vol. xxiv, 1910. 
[Annals of Botany, Vol. XXV. No. XCVIIX. April, 1911.] 
