586 Saxton . — Contributions to the 
the pollen-tube has begun to penetrate the apex of the nucellus (Fig. 27) 
shows the tube nucleus and the generative cell still enclosed in the spore 
cavity, the generative ceil being still attached to the spore wall. A some- 
what later stage (Fig. 28) shows the tube nucleus some way down the tube, 
and the generative cell lying free in the spore cavity. Shortly after, the 
upper part of the tube is found to be empty, while three nuclei, embedded 
in a common mass of cytoplasm, are found close to its tip. The sterile 
nuclei (tube and stalk nuclei) are exactly alike, and lie, as usual, side by side, 
and in advance of the body nucleus (Fig. 29). The body nucleus gradually 
increases in size, and a part of the cytoplasm soon becomes differentiated 
around it to form a definite body-cell (Fig. 30). Finally, the body-cell 
divides to form two hemispherical male cells. Whether these were enclosed 
in a mother-cell wall could not be determined. Some aspects of the mature 
pollen-tube are shown in PL XLV, Figs. 41, 42, and PI. XLVI, Fig. 64. It 
is worth noting that the two male cells may be placed either side by side 
or one vertically above the other (Figs. 41 and 64), the former being the 
usual arrangement in the Cupressoi'deae. There is some evidence that the 
male cells do not always become spherical when mature, as they usually 
do in Cupressoideae ; at any rate a male cell which is still hemispherical 
has been seen inside an archegonium, and no case has been seen where it 
could be stated with any certainty that the male cells were spherical in the 
pollen-tube. 1 
The Megasporangiate Strobilus and the Female Gametophyte. 
The young female cones of Tetraclinis are very similar to those of 
Widdringtonia , especially W. juniper oides, as shown in Text-fig. 1. They 
are borne singly on very short lateral 
branches, and each consists of two pairs 
of widely spreading cone scales. In 
the centre of the cone are seen six 
(rarely four or eight) erect ovules, with 
rather long tubular micropyles. The 
insertion of one pair of scales is 
slightly below that of the other, and 
the scales of the upper pair are usually 
sterile, all the ovules being attached 
to the two lower scales ; when, how- 
_ . „ ever, eight ovules are present, two of 
Text-fig. i. — Drawing of a young cone 
of Tetraclinis as seen from above, x 15. them are inserted on the upper pair. 
A P nl 2 4 * A median longitudinal section of 
1 Some cases of male cells circular in section have been seen, where the two were cut successively 
in serial sections, but such an appearance is also characteristic of hemispherical cells, when cut more 
or less parallel to the flat side. 
