GYMNOSPERMS. 165 



FECUNDATION. 



Goroschanken ('83) observed in Pinus pumilto that both male nuclei 

 pass into the egg-cell, and the same fact was established for Picea 

 -vulgaris by Strasburger ('84). Dixon ('94) seems to have been the 

 first to observe that in Pinus syhestris all four nuclei in the pollen 

 tube, i, e., the two male nuclei, the stalk-cell nucleus, and the tube 

 nucleus pass into the egg-cell of the archegonium. This fact has been 

 confirmed by Blackman ('98) for Pinus sylvestris, by Murrill (1900) 

 for Tsuga canadensis , and by Ferguson for Pinus strobus. Accord- 

 ing to Blackman the behavior of the four nuclei in Pinus sylvestris 

 can be easily followed after their entrance into the egg-cell. The two 

 male nuclei around which the cytoplasm of the generative cell can be no 

 longer observed are distinguished by their larger size. In P. strobus 

 one of these nuclei is sometimes larger than the other (Fig. 68, C). 

 The nuclei of the stalk cell and tube are, however, similar, and can 

 scarcely be distinguished from each other. 



Within the egg one of the two male nuclei moves toward the nucleus 

 of the egg, the other three nuclei remaining near the upper end of the 

 cell. On its way through the cytoplasm of the egg the functional 

 male nucleus increases in size, and in some cases in substances stain- 

 ing more readily, but in others the increase in size seems to be due to 

 vacuolation. The nucleus of the egg-cell in Pinus sylvestris at the 

 time of fecundation presents a strikingly peculiar structure, which 

 differs from that of the female nucleus in all other plants. After the 

 formation of the ventral canal-cell the female nucleus migrates toward 

 the center of the cell, and, by the time it has reached the middle, it 

 has attained an enormous size, and there is developed within it a rather 

 coarse, uniform, and wide-meshed linin reticulum which persists until 

 a later stage (Fig. 69, A). Within this linin reticulum the chromatin 

 is distributed in irregular masses of varying size. These masses may 

 be in the form of irregular lumps as if composed of an aggregate of 

 granules, or in shreds or rods with uneven edges. Sometimes they 

 appear globular as small nucleoli. In fact it is quite difficult to distin- 

 guish between some of the small nucleoli and similar chromatin masses, 

 if, indeed, a difference really exists. The quantity of chromatin in the 

 nucleus is proportionally very small. In addition to the linin reticulum 

 there is also present a fine granular substance which appears to be 

 evenly distributed in the nucleus or aggregated along the linin threads. 

 In the former case the nucleus appears more uniformly granular, and its 

 linin reticulum stands out less sharply. The structure of the egg- 

 nucleus in Pinus sylvestris, as described by Blackman, agrees with 



