Oct., 1921.] 



TAKAMINE :~LIFE HISTORY OF ISOETES. 



185 



the sporophylls and put in fresh water, the microspores and macro- 

 spores being kept in separate dishes. 



The fresh water being renewed from time to time, they are to 

 be left until the spermatozoa are mature and ready for discharge, 

 and the macrospores show their three ribbed opening at the tetra- 

 hedral edge of silicified outer layer of the membrane. The fertilization 

 takes place in nature in May in Tokyo. The spores collected in 

 November and kept in culture in a green house or in a thermostat, 

 ripe early in winter (11). The maturity of the spermatozoa may 

 be conveniently tested under the microscope by the use of a lowpower 

 objective, e. g. Zeiss B. by the addition of a drop of water saturated 

 with coiwmon coal gas, when all the mature spermatozoa are dis- 

 charged in a few seconds ; ethylether, carbonmonoxide as well as 

 ethylene, acetylene, and other unsaturated hydrocarbons may be used 

 for the same purpose in a gaseous form or as an aqueous solution as 

 has been first made known to us by Fqjii (8). 



Gametophyte, Fertilization and Embryoformation 



The spermatozoa live very short time after they are once discharg- 

 ed, usually only five to ten minutes swimming in water ; but while 

 they are in antheridia they live pretty long duration, some of them 

 being alive more than one year. 



In a female gametophyte five or six archegonia are developed in 

 general, though sometimes more than ten archegonia in a gameto- 

 phj'te are met with. 



At the stage, when the arche- 

 gonium is ready for fertilization, 

 the plasma of the neck canal cell 

 and of the ventral canal cell 

 stains deeply with haematoxylin, 

 and can be distinguished clearly 

 from other cells, and the contents 

 of these cells degenerate, as is 

 common in Lycopodiales. 



Sometimes there are two 

 nuclei in the neck canal cell (Text- 

 fig. 1), as a result of division of 

 one nucleus without being fol- 

 Text-fig.l. Archegoniumof/.japomca, j^^^^ , ^^^ formation of the 



with two nuclei in the neck canal cell 



{.DDxCoraps. 8). 



divisionwall. 



