Stiles . — The Podocarpeae. 479 
P. macrophyllus the egg just before fertilization (PI. XLVIII, Fig. 31) is 
about 45 /x or 50 \x in diameter. 
Before fertilization takes place the nuclei of the prothallus cells begin 
to divide, but the products of division are not cut off by cell-walls, and as the 
process may be and generally is repeated more than once, the prothallus 
cells in the old seeds may contain as many as eight nuclei. This is 
evidently a phenomenon of general occurrence in the genus, as it takes 
place in all species that have so far been examined, namely, P. coriaceus by 
Coker, and P. nagi , P. macrophyllus , P. elatus , and P. latifolius , by the writer. 
The development of more than one megaspore in an ovule is a 
phenomenon that has been observed in several Coniferous genera; 1 it has 
been recorded for Podocarpus by Coker in P. coriaceus . 2 In both P. latifolius 
and P. macrophyllus an example of this has been found among the writer’s 
material ; in the former case the prothalli were in a young stage before wall 
formation had commenced, but in the case observed in P. macrophyllus both 
prothalli had produced archegonia, and one contained a pro-embryo. 
In Phyllocladusp Saxegothaeaf Microcachrysp and Dacrydium laxi - 
folium 6 a thick megaspore membrane of the usual type is developed, but 
in the two species of Podocarpus examined by Thomson, P. coriaceus and 
P. macrophyllus , subsp. maki (P. Makoyi, P. chinensis , or P. sinensis ), no 
trace of a megaspore coat could be found. From the species examined in 
the course of this work it is evident there is great variation in the genus as 
regards this structure. In P. macrophyllus and P. nagi the membrane is 
very poorly developed, and never appears to be more than 1 /x thick. Only 
an isolated late stage has been observed in the case of P. elatus , and here 
also the membrane was very poorly developed. P. latifolius , on the 
other hand, is in marked contrast to these species. At about the 32- 
nucleate stage of the prothallus the megaspore membrane is well under 
1 /x thick, while by the time the neck-cells are cut off from the central cells 
of the archegonia the membrane forms a thick coat about 4-2 /x thick. It 
thins out towards the apical part of the prothallus, and is not more than 
2 fx thick in the region of the archegonia. By the time the pro-embryos 
are developing the membrane becomes thinner, and is then about 2-5 /x thick 
in the middle region of the prothallus. 
x. Male Gametophyte. 
A. Early History (Structure of Pollen). 
The early history of the male gametophyte, from the microspore stage up 
to the time of shedding of the pollen, has been investigated in species of all 
genera of the Podocarpeae except Pherosphaera. The later history from 
1 e. g. Sequoia (Lawson, ’04 1 , p. io) ; Callitris (Saxton, ’10, p. 559 )'. 
2 Coker (’02), p. 97 . 3 Young (’10), pp. 86 , 88 . * 4 Noren (’08), p. 115 . 
6 Thomson (’09 2 ), p. 349 . 6 Thomson (’05 1 ). 
