232 THE AMERICAN NATURALIST. [Vol. XXXIX. 



zo5logists have been able to do in some favorable animal types 

 (Montgomery, Sutton, Moenkhaus). The chromosomes divide 

 longitudinally in the usual way, the halves being drawn apart 

 from the points of attachment of the spindle fibers (Fig. 17, e) . 

 It is clear that each daughter nucleus receives a full set of 24 

 daughter chromosomes, 12 of paternal and 12 of maternal 

 origin, and. that there is about an equal amount of chromatin 

 from each sex. 



It should be especially noted that in the process of fertiliza- 

 tion in the pine there is at no time present what is generally 

 called a fusion nucleus, i. e., a single nucleus whose membrane 

 incloses all the material of both male and female gamete nuclei. 

 Such fusion nuclei, as we shall see, have been reported many 

 times in other groups of plants than the gymnosperms where in 

 many cases, however, detailed studies are very difficult and can 

 scarcely be said to have even approached our knowledge of the 

 pine. 



Studies of other botanists indicate that the gymnosperms 

 generally will show essentially the same conditions as in the 

 pine. Thus Woycicki ('99) distinguished in Larix two groups 

 of chromatin which he regarded as paternal and maternal. And 

 Murrill (: 00) states for Tsuga that the chromatin of sperm and 

 egg remain separate, forming two spirems, and only after their 

 segmentation into chromosomes are the two sets of structures 

 brought together in the first cleavage spindle. Land (: 02) 

 figured the sperm nucleus of Thuja imbedded in a depression of 

 the egg nucleus. Miyake (: 03a) noted that the sperm nucleus 

 of Picea became more or less imbedded in the egg nucleus while 

 the nuclear membrane remained intact, and the same author 

 (Miyake, :03b), reports similar conditions in Abies. Robert- 

 son (: 04) figures the sperm nucleus of Torreya lying within a 

 depression in the female and with a large amount of granular 

 cytoplasm (kinoplasm) at the side. Coker (:03) states that 

 the partition between the gamete nuclei of Taxodium " does 

 not entirely disappear until immediately before the first divi- 

 sion " although the two structures are closely united for some 

 time previously while they pass to the bottom of the &gg. 



Lawson, studying Sequoia (:04a) reports gamete nuclei of 



