10 
Miyake, The development of the gametophytes etc. 
hamia agree on ttie whole with the description of Miss Ferguson. 
As the first prothallial cells elongate toward the center of the va¬ 
cuole, they divide several times by cross walls before reaching the 
center of the cavity. A part of the prothallial tissue as they half 
way advanced toward the center of the vacuole is shown in fig. 57. 
The filling up of the central vacuole with growing prothallial 
tissue proceeds rather rapidly, and in about a week after the first 
wall-formation the whole megasporic or embryo-sac is filled with 
solid tissue. The stage just after the formation of the solid pro¬ 
thallial tissue is shown in fig. 58. Arnoldi (1900), Coker (1903), 
Lawson (1904) and several other recent investigators, confirming 
an earlier Statement of Strasburger (1880), have noted many 
nuclei in each of the young prothallial cells. Miss Ferguson 
(1904), however, has “not observed multinucleated cells in 
the prothallium of Pinus up to the time when the suspensor 
has elongated and carried a several celled embryo to a considerable 
depth into the endosperm.” Sheadds: “There is offen an appearance 
of inore than one nucleus in a cell, but careful study never fails 
to demonstrate a delicate cell-wall between the nuclei. At an 
early stage in prothallial development the cell-walls are very de¬ 
licate, scarcely more than condensations of the ectoplasm so that 
they might easily be mistaken, in Pinus , for Strands of cytoplasm. 
Doubtless the cells become plurinucleated during a more advanced 
stage in embryo formation.” I have also failed to find multi¬ 
nucleated cells in young prothallium of Cunninghamia , but in the 
older prothallium, some of the cells seemed to contain more than 
one, usually two, nuclei in each. Careful study has sometimes 
proved that some of those cells are only apparently bi- or multi¬ 
nucleated, a very delicate wall being found between the nuclei. 
Thus most of the cells of the mature prothallium were found to 
be uninucleated. 
It was often maintained that the nuclear division in the pro¬ 
thallium is sometimes amitotic. Mlle. Sokolowa (1890) makes 
a similar Statement in her studies on the prothallium-formation 
of various Gymnosperms. Noren (1907) mentions that “Diese 
Teilung (division of the first prothallial cells) ist oft amitotisch, 
was auch von Sokolowa erwähnt wird”. Coker (1903), on the 
other hand, states that “these nuclear divisions are generally, at 
least, of the mitotic type”. So far as my Observation goes, the 
division takes place mitotically, and no case was come across in 
which the nucleus showed a sign of amitosis. 
The wall enclosing the female prothallium, or the megaspore- 
membrane is at first thin and delicate. During the growth of the 
prothallium the membrane becomes thicker and more conspicuous. 
Fig. 51 shows the female prothallium just before the wall-formation 
and the megaspore-membrane is found about half way thickened. 
In figs. 53 and 54 the double nature of the membrane, as clearly 
pointed out by Thomson (1905) in other Gymnosperms, is more 
prominent. In the mature prothallium, the exosporium shows 
characteristic radial striations and is several times as thick as the 
