8 
Mijake, The development of the gametophytes etc. 
Carothers (1907) reports that in the early stages of the growing 
female prothallium of Ginkgo, the diyision of the free nuclei is 
simultaneous, but later free nuclear divisions proceed irregularly. 
The question whether this is normalty so in Ginkgo or represents 
rather an abnormal case, remains to be inyestigated. Her material 
was subjected to “unnatural condition — growth after Separation 
from the tree — although an effort was made to render conditions 
as natural as possible”, and the anthor herseif admits that the 
latter alternative is not impossible. 
It is nsnal in the Coniferae , that in each oyule, a single 
megaspore develops into the female prothallium, and I have never 
found a case in Cunninghamia where the ovule contained more 
than one prothallium. Arnoldi (1900),- however, found that more than 
one prothallium are sometimes developed in the ovule of Cunning¬ 
hamia, and figures as many as five young prothallia of yarious sizes in a 
single ovule (Arnoldi, 1900, texfig. 5). In Cryptomeria Lawson 
(1904 b) found that only one out of twelve or sixteen potential 
megaspores germinates and there is consequently but one pro¬ 
thallium formed. Coker (1903) found that in Taxodium only a 
single prothallium is usually formed, but one case was found in 
which the nucellus contained two young prothallia. Hofmeister 
(1851) mentions the occasional presence of two prothallia in Pinus 
sylvestris and Taxus haccata. It was since confirmed by Farmer 
(1892) for Pinus and by Strasburger (1904) and Coker (1904) 
for Taxus. Coker (1902) has also found two prothallia in the 
young ovule of Podocarpus. In Sequoia (Arnoldi, 1899a, 1899b; 
Lawson, 1904 a) there are usually more than one prothallium or- 
ganized, and as many as eight has been counted in a single ovule; 
one of them enlarges more rapidly than others and form the pri- 
mary prothallium, while one or two secondary prothallia, though 
failing to produce true prothallia! tissue, nevertheless reach an 
advanced stage of development. In this respect Sequoia differs 
from other Conifers where the single prothallium seems to be the rule. 
Early in the development of - the young prothallium, it is 
surrounded by two to four layers of larger cells or tapetum. Each 
cell of the tapetum has a larger nucleus and denser cytoplasm 
when compared with the surrounding cells of the nucellus (figs. 46, 
108). The presence of the tapetum-tissue in Cunninghamia has 
already been observed by Arnoldi and is figured in his paper 
(Arnoldi, 1900, textfigs. 4 and 5, PL XVII, hg. 2). A similar ta¬ 
petum was found in Taxodium by Coker (1903), while it is re- 
ported by Lawson (1904 b) to be absent in Cryptomeria. 
The origin of the tapetal layer has been differently interpretted 
by various investigators. Lang (1901) designates a similar tissue 
in Stangeria as sporogenous cells. Thomson (1905) considers that 
in all G-ymnosperms whose megaspore-membrane belongs to a normal 
type have the tapetum originated from the sporogenous tissue. 
Noren (1907) agrees with the above mentioned authors in re- 
garding the tapetum-cells in Juniperus as sporogenous in origin. 
Coker (1903) on the other hand, is inclined to take the tapetal 
