Ovule of Bowenia spectabilis. 637 
part 0*4 mm. long, fitting closely into the micropylar tube (Fig. 11, PI. LXI). 
This part is shrivelled and black in colour, as are also a few of the outer 
cells of the lower, expanded part of the nucellus. Below the beak-like 
portion the tissue of the nucellus is hollowed out and forms a large chamber, 
which in some ovules extended completely through the nucellus, and so was 
in direct communication with the prothallus. In others the lower part 
of the nucellus was intact and no such communication had been established 
(Fig. 14, PI. LXI). In this large lower cavity numerous pollen-grains were 
growing, sometimes as many as twenty in one ovule, and all at approxi- 
mately the same stage of development (Fig. 15, PL LXI). In Zamia, on 
the contrary, pollen-grains at almost all stages of development may be found 
in one nucellus. The pollen-grains have produced long, unbranched, 
rooting ends which have penetrated the wall of the cavity and into the 
nucellar tissue (Fig. 14, PI. LXI). They run out horizontally from the 
cavity, and before reaching the surface turn downwards and run just below 
the epidermis. At the end of each root-like growth is the tube nucleus. 
When viewed from above the tubes appear as dark lines radiating from 
a central point. The end of the tube in the cavity is much swollen and 
contains the developing fertilizing apparatus. It consists of two prothallial 
cells and a large terminal generative cell (Fig. 1 5, PI. LXI). The first pro- 
thallial cell is next. to the pollen-grain coat. It has a fairly large nucleus 
and its wall bulges considerably into the second prothallial cell, whose 
nucleus is thus pushed to one side, and the two thus give the appearance 
of one cell within another. At the end of the second prothallial cell is the 
large generative cell, which contains a nucleus 0-03 mm. in diameter (Fig. 16, 
Pl. LXI). The chromatin of the nucleus is arranged in a definite network, 
and there is a nucleolus o-oi 5 mm. in diameter. Situated at opposite ends of 
the nucleus, generally opposite to an indentation in its margin, are the two 
blepharoplasts. They are homogeneous bodies with numerous fine radiations 
arising from them on all sides. When stained with Heidenhain’s haema- 
toxylin blepharoplasts and radiations take an intense black. In some cases 
the pair lie in the plane of the long axis of the pollen-tube, in other cases 
in a plane at right angles to it. 
This is the only stage in the development of the fertilizing apparatus 
that has been obtained, but the whole structure is so similar to that which 
has been described for Zamia 1 and Dioon 2 that it is evident that develop- 
ment has taken place in the same way as in those where the divisions have 
been followed. 
The female prothallus appears as a white glistening mass with a ring 
of five to seven archegonia opening into an archegonial chamber, which is 
1 Webber : Spermatogenesis and fecundation of Zamia. U. S. Dept. Agric. Bull., Bur. Plant 
Ind., vol. ii, 1901. 
2 Chamberlain : Spermatogenesis in Dioon edule . Bot. Gaz., vol. xlvii, 1909. 
