FERTILIZATION 



295 



a conspicuous part in the formation of this "mantle." This phenomenon, 

 the significance of which can only be conjectured, is found in Taxodium 

 (Coker 1903), Torreya calif ornica (Robertson 1904), Torreya taxifolia 

 (Coulter and Land 1905), Cephalotaxus Fortunei (Coker 1907), Ephedra 

 (Berridge and Sanday 1907; Land 1907), Phyllocladus (Kildahl 1908), 

 Juniperus (Nichols 1910), Agathis (Eames 1913), and Taxus (Dupler 

 1917). 



Chromosome Behavior. The behavior of the chromosomes during 

 the fusion of the sexual nuclei and the first embryonal division has 

 been described in a number of conifers. As a general rule, to judge from 

 the data at hand, the chromatin contributions of the two pronuclei do 

 not become intimately associated in the fusion nucleus, but remain 

 distinguishable until the first embryonal mitosis occurs. Each of the 

 pronuclei then gives rise to its complement of chromosomes which 



B f 



FIG. 120 Fertilization in Pinus. 



A, male nucleus pressing into female nucleus. X 140. B, first embryonal mitosis, 

 showing separate paternal and maternal chromosome groups. X 472. (After Ferguson, 

 1904.) 



become arranged, often as two separate groups, upon a common 

 spindle. Such an independent formation of the male and female 

 chromosome groups has been observed in Pinus (Blackman 1898 ; Cham- 

 berlain 1899; Ferguson 1909, 1904) (Fig. 120), Larix (Woyciki 1899), 

 Tsuga candensis (Murrill 1900), Juniperus communis (Noren 1907), 

 Cunninghamia (Miyake 1910), and Abies (Hutchinson 1915). In 

 Sequoia, on the other hand, Lawson (1904) reports that the two nuclei 

 form a common reticulum in which the male and female constituents 

 cannot be distinguished. With regard to the first embryonal mitosis 

 the general opinion has been that all the chromosomes, paternal and 

 maternal, split longitudinally, the daughter chromosomes being distri- 

 buted to the daughter nuclei as in any other somatic mitosis. This 

 type of behavior was described for the chromosomes of Pinus by Miss 

 Ferguson (1904) and at once came to be regarded as general for coni- 

 fers, as it had been for other organisms. 



A new interpretation differing in certain fundamental points from the 

 above has been more recently suggested by Hutchinson (1915), as a result 



