Fertilization in Pinus Str obits. 
461 
a phenomenon as that described by Arnoldi could have 
escaped detection ; and I must, therefore, conclude that it 
does not take place in the species of pines which I have 
studied. 
Some interesting observations have been made, however, 
regarding the nature of the nucleolus of the egg-nucleus. As 
already indicated, this nucleolus does not arise in Pinus Strobus 
until the egg-nucleus has attained considerable size. It appears 
in the lower part of the nucleus as a minute, solid, spherical 
body ; during growth a small, central vacuole appears, then 
other vacuoles, until, at maturity, it is completely filled with 
vacuoles of various sizes (Figs. 32-36). A limiting membrane 
is not always apparent in this nucleolus (Fig. 80, PI. XXV) ; 
but, in some instances, there seems to be very strong evidence 
of such a membrane (Figs. 36, PI. XXIV, and 90, PI. XXIII). 
In Fig. 36 the nucleolar wall has been broken at one 
place, and a vacuole, lying near the point of rupture, 
has been indented along its outer surface, thus becoming 
crescent-shaped. Montgomery (’ 98 ) sounded a word of warn- 
ing against interpreting the peripheral stratum of the ground- 
substance of the nucleolus as a wall-layer ; and there is a 
possibility that, in the figures above referred to, what appears 
like a limiting membrane is only the outer, unmodified portion 
of the nucleolus. 
The attitude of this nucleolus towards dyes varies much 
at different periods in its history. It may or may not take 
the safranin stain characteristic of Flemming’s triple com- 
bination ; it may stain intensely with gentian-violet or 
iron-hematoxylin (Figs. 36, PI. XXIV, and 88, PI. XXIII) ; 
it may show a weak reaction to these stains (Fig. 90, PI. 
XXIII), or it may be absolutely unaffected by them, remain- 
ing as a hyaline or greenish-yellow structure (Fig. 89, PI. 
XXIII). When the nucleolus resists the action of dyes, its 
nucleus is usually totally free of the secondary nucleoli, which 
have been described in connexion with the maturation of the 
egg— nucleus, and the cytoplasm of the egg is studded, to an 
unusual degree, with large, deeply staining granules. But 
