510 Ber ridge. Fertilization in Ephedra altissima . 
While in process of division, however, to form the egg and ventral 
canal nuclei, it is very inconspicuous owing to the diffuseness of the spindle 
and slenderness of the chromosomes, which number about twelve. The 
spindle is parallel to the long axis of the archegonium, and is limited at 
the sides by a series of vacuoles. The egg nucleus is usually somewhat 
larger than the ventral canal nucleus, but otherwise, when first formed, 
they resemble one another very closely. The former retreats into the 
egg-cell, but the latter remains close to the neck, and, like the synergidae 
of the Angiosperms, is either pushed aside or broken up by the entry of 
the pollen-tube ; in cases where no tube reaches the egg-cell it sometimes 
outlives the egg nucleus itself. 
The earlier stages in the germination of the pollen-tubes could be 
followed within the pollen chamber, for the grains in the majority of cases 
germinate on the surface of a drop of liquid, the fixed remains of which 
form a structureless film across the mouth of the chamber. The pollen- 
grain shown in Fig. 2 occurred in some material of E. distachya collected 
by Miss Sanday in Brittany ; it shows the intine escaping from the exine, 
and indicates that the body cell has already divided, while still within the 
grain, into two equal gametes, as described by Dr. Land for E. trifurca. 
Fig. 3 a shows a slightly later stage in the development of the pollen- 
tube in E. altissima, while in Fig. 3 b the tube has elongated considerably ; 
in this case the stalk-cell could not be traced. All these three figures 
show the two gametes enclosed in a well-marked, but not very dense sheath 
of cytoplasm, and in this they appear to travel through the neck down to 
the egg-cell, for in Fig. 4, where the tip of the tube is in actual contact 
with the wall of the egg-cell, the nuclei still occupy the same relative 
positions, and some trace of the sheath is still to be seen. In this last case 
this pollen-tube has been forestalled by another, which has evidently caused 
great disturbance of the cytoplasm of the egg ; the ventral-canal nucleus 
has been broken up and swept aside by the inrush of the contents of the 
pollen-tube. 
Figures 2, 3 a , and 4 are all drawn to the same scale and illustrate the 
increase in size of the two gametes as they pass down the tube. Their 
average diameter in Fig. 3# is 10 /z, in Fig. 4 it is 14 /q while of those 
represented in Fig. 5 within the archegonium and drawn on a smaller 
scale, the first sperm ( m 2 ) measures about 19 /z, and the second male gamete 
(m 2 ) } which is probably beginning to enlarge and degenerate, about 21 \i in 
diameter. The statement was made in a previous paper 1 that the male 
gametes are unequal in E. distachya ; in several pollen- tubes they appear 
distinctly unequal ; the second one, however, is usually very irregular in 
shape, and shows signs of breaking up into two or more. That fragmentation 
1 E. M. Berridge and E. Sanday. Oogenesis and Embryogeny in Ephedra distachya. New 
Phytologist, vi, 5, 6, 7, 1907. 
