THE HIGHER CRYPTOGAMIA. 343 



of very fine cilia attached to the two front coils of the spiral 

 may be distinguished under favorable illumination (PL 

 XL VI, figs. 16, 17). The addition of colouring matter to 

 the water in which the spermatozoa are moving, shows that 

 during the life of the latter these cilia oscillate actively. 

 The duration of the motion of the spermatozoa of Isoetes 

 never exceeds three hours according to my observations. 



Microspores sown at the end of August produced the 

 first spermatozoa in the middle of September. The pro- 

 duction of spermatozoa lasted until January. The water 

 of the vessels in which I sowed the large and small spores, 

 swarmed with spermatozoa on some days in the middle 

 of October. At this time the thinly -fluid mucilage which 

 fills the canal of the mouth of ripe archegonia, often con- 

 tained thread-like bodies of a firm mucilaginous substance, 

 which might be the remains of spermatozoa, whose motion 

 had ceased. 



The first indication of the commencement of the develop- 

 ment of an embryo in an archegonium, is the division of 

 the impregnated germinal vesicle by a transverse septum, 

 somewhat inclined to the longitudinal axis of the archego- 

 nium (PL XL VI, figs 18, 20). During the formation of 

 this septum the germinal vesicle expands, often to some 

 extent, in a direction at right angles to the longitudinal 

 axis of the archegonium. After the disappearance of the 

 primary nucleus of the cell and the appearance of two new 

 nuclei, the lower of the two halves of the impregnated 

 germinal vesicle, and afterwards the upper half also, is 

 divided by a septum cutting the first formed septum at a 

 right angle (PL XLVI, fig. 21). The rudiment of the embryo 

 of the new generation, when consisting of from two to four 

 cells, has the form of a procumbent oval ; when viewed in the 

 direction of its longitudinal axis (Plate XLVI, figs. 18, 19), 

 it appears not longer than the unimpregnated germinal 

 vesicle. But owing to its longitudinal expansion, it has 

 already began to penetrate destructively into the tissue of 

 the prothallium. 



As in many similar cases, the cells of the prothallium 

 which immediately adjoin the rudimentary embryo, exhibit 

 a somewhat active multiplication before they become 



