LIFE HISTORY OF PINUS IOI 



fication, it does not show, in normal conditions, a true granular 

 structure; but it may present a most delicate, interrupted, 

 granular network ; or, it may consist of large, irregular, dif- 

 fusely-staining masses which are united into an imperfect reticu- 

 lum (figs. 206, #, and 206,^). In the latter instance the 

 chromatic granules are either too minute to be distinguished, or 

 they have been dissolved in the linin ground-work. The linin, 

 always very abundant in this nucleus, may form heavy hyaline 

 cords, on which the chromatin is collected at irregular intervals 

 (figs. 206, , and 206, f) ; but it more often consists of less con- 

 spicuous strands (figs. 206, 3, to 206, d). Great as are the vari- 

 ations in the structure of this nucleus, its chromatin has always 

 been found, in the species of pines which I have studied, to 

 exist either in the form of irregular granules of varying sizes, 

 or apparently dissolved in the liniri. Such a resolving of the 

 chromatin into nucleoli as that described by Chamberlain ('99) 

 in Pinus Laricio and illustrated in his figs. 14 and 15 has not 

 been observed in normal nuclei by the writer. 



Whether the various appearances presented by the egg-nucleus 

 represent normal phases in its life history, or whether one is 

 normal and the others are artifacts resulting from the action of 

 fixing agents, is, of course, a mere matter of conjecture. But, 

 inasmuch as these different aspects are characteristic of this 

 nucleus during its period of growth, also after it has to all 

 appearances reached maturity, and again at the time of its con- 

 jugation with the sperm-nucleus, it seems reasonable to conclude 

 that all are normal and correspond to definite physiological 

 processes, which take place within the nucleus. Hertwig's 

 ('98) interesting experiments on fed and unfed Actinosphcerium 

 are in point here. They seem to show conclusively that the 

 structure of a nucleus varies with the character of the work 

 which is being done by it. 



Strasburger ('84) described the nucleus of the oosphere in the 

 Abietmece as being densely filled with a granular substance which 

 entirely obscured or masked the chromatin. This substance he 

 called metaplasm, and virtually considered the nucleus a vacuole 

 filled with a nuclear sap capable of taking up or elaborating this 

 material. Ikeno found a similar substance in the sexual nuclei 



