Nos. 451-452.] STUDIES ON THE PLANT CELL. 



59 1 



eggs has been done on this group (to be treated in Section IV). 

 Passing over earlier investigations that described accurately the 

 general structure of the egg of gymnosperms we shall consider 

 the results of a number of comparatively recent papers that 

 treat especially the pine, spruce (Picea), hemlock (Tsuga), fir 

 (Abies), cycads, Ginko, Gnetum, Taxodium, etc. 



Oogenesjs and fertilization in the pine has been the subject of 

 several extensive studies the chief being papers by Dixon ('94), 

 Blackman ('98), Chamberlain ('99) and Ferguson (:oib). The 

 protoplasm of the egg is at first vacuolate but later takes on a 

 denser structure which becomes very puzzling because of numer- 



-/. s 



FIG. ii. The Egg. a, Daphne, showing leucoplasts ; b, oedogonium, showing 

 receptive spot; c, pine, with numerous proteid vacuoles ; d, embryo sac of the 

 lily, gamete nuclei fusing, remains of one Synergid (s) shown, (a, after Schim- 

 per, '85; b, Klebahn, '92; c, Ferguson, :oi.) 



ous granular inclusions and masses of amorphous material which 

 together with fibers present a very complex texture. The 

 fibers are sometimes collected in fascicles and they may form a 

 sort of weft at the periphery of the egg or radiate out from the 

 nucleus which is generally surrounded by a kinoplasmic sheath. 

 The complexity is greatly increased as the egg grows older by 

 the development of remarkable structures called proteid vacuoles 

 (See Fig. 1 1^) which have been especially described by Blackman 

 and Ferguson. The number of proteid vacuoles is exceedingly 

 variable in the egg but they sometimes fill three fourths of the 

 structure. They are spaces in the cytoplasmic reticulum filled 



