SEXUALITY IN THE LOWER CEYPTOGAMIA. 71 



more than half au hour, the rotation ceases: the motion of the 

 spermatozoa lasts somewhat longer, but is less active, and they also 

 eventually become quiescent. 



After the spores have been in contact with the spermatozoa 

 the former become clothed with a plainly visible membrane,* and 

 shortly afterwards septa are formed and germination commences. 

 Those spores which have not been in contact with spermatozoa remain 

 unchanged for some days and ultimately decompose. Sometimes a 

 membrane is formed over them, and a kind of imperfect germiua- 

 tion commences, but this only lasts for a few days, after which 

 the spores decay in the same way as those in which no membrane 

 was formed. 



Fucus serratus, L. and Fucus nodosus, L. (Ozoihallia vulgaris j 

 Dene and Thur.) yielded M. Thuret the same results, except that 

 in the latter species the contents of the sporangium form four, not 

 eight spores as in F, vesiculosus. 



The intermixture of the spores of F. nodosus with the sperm^atozoa 

 of F. serraius and vesiculosus, and of the spores of the two latter 

 with the sj)ermatozoa of the former yielded no results, although 

 the spermatozoa attached themselves to the spores and produced 

 the ordinary movement of rotation. Neither could the spores of 

 Himanthelia lorea be impregnated by the spermatozoa of Fucus 

 nodosus or F. serratus. The spores of F. serratus, could not be fer- 

 tilized by the spermatozoa of F. vesicvhsus, but strange to say, on the 

 inverse operation, i. e., when the spores of F. vesiculosus were mixed 

 with the spermatozoa of F. serratus, the spores germinated. Upon 

 these facts, M. Thuret observes, that F. nodosus, Himanthelia lorea, 

 and F. serratus, are very constant in their form, wliilst F vesiculosus 

 is extremely variable, and he thinks it not improbable that the great 

 variability is owing to the facility with which the latter species is 



occurring when spores are examined under the microscope he explauis by attribut- 

 ing it to the concentration of a much greater number of spermatozoa than could 

 ever be found in the same space in nature. At the same time he considers the 

 rotation as not altogtlier accidental, for he found that the spermatozoa of Fucus 

 communicated no rotation to some spores of Florideee, which were small enough, 

 and round enough to have been easily set in motion, and as a matter of precaution 

 in experiments he recommends the application of a sufficient nimiber of sperma- 

 tozoa, to render the rotation manifest. 



* The formation of this membrane, is said to commence six or eight minutes 

 after the contact of the spore with the spermatozoa. See Beuxieime note sur la 

 fecondation des Fucades. A. S. N. 4. Ser. Yol. vii. p. 35. 



