1909] 



YAMANOUCHI— MITOSIS IN FUCUS 189 



(fig. 58) and third (fig 



In the 



first division of the fertilized egg there are 64 chromosomes arranged 

 in the equator. Thus, the number is constantly 32 and 64 in Fucus 



esiculosus. 



Willi 



>phyll 



estimated in the mitotic 



nium mother cell is about 26-30, and later on they counted in the 



14-15 as the reduced number. Stras- 



omum 



burger (24) considers 30 to be the probable number in Fucus 



platycarp 



number 



of the same genus or in allied forms 



— _ _ — w 



has also been known in other cases ; for instance, in Osmunda, where 

 Osmunda regalis has 12 and 24 chromosomes and O. cinnamomea 



22 and 44 



Hon of generations.— -It has been suggested by Strasburger 

 (26) that the antheridia and oogonia in young stages (Anlagen der 

 Oogonien und Antheridien) should be regarded as corresponding not 

 with antheridia and oogonia of Dictyota but with its tetrasporangia, 

 although the exact phenomena of reduction which occurs in the first 

 two divisions in these structures was not then known in detail. The 

 Present result may confirm the correctness of his suggestions. 



Briefly summarizing the nuclear conditions of Fucus: The 

 vegetative cells of the plant contain 64 chromosomes, and the same 

 number is present up to the formation of antheridium and oogonium 

 lnitials - In the first nuclear division in these initials 32 chromosomes 

 appear, the reduced number, but they are bivalent. At the telophase 

 of the second division there are 32 univalent chromosmes. Conse- 

 quently, the four nuclei resulting from the second division in both 

 oogonium and antheridium initials are the first nuclei which contain 

 32 univalent chromosomes. Each of the four nuclei divides further 

 ^thm these structures, once in the oogonium and four times in the 

 antheridium, and after the division or divisions 'there result 8 

 nuclei or 64 sperm nuclei, each nucleus containing 32 chromo- 

 *°«s- At the union of the sperm and egg nuclei, the number is 

 r ubled » a nd the sporeling with the diploid number of chromosomes 



e gg 



develop 



s into a Fucus plant. 



