424 Lawson. — The Gametophytes , Fertilization and 
immediately surrounding them. Their nuclei increase correspondingly, 
and become very conspicuous when compared with the small nuclei of the 
sterile tissue. There are always one or two large, deeply staining nucleoli 
present, and the chromatin is in the form of small granules suspended on 
a network of linin as shown in Fig. 12 . 
There are usually three or four sporogenous cells differentiated, and 
these are always situated near the base of the sporangium just a little 
above the point of insertion of the integument. The position and relative 
size of the sporogenous cells is well shown in Fig. 11 . According to 
Coker (’03) but a single megaspore mother-cell is organized in Taxodium. 
In this respect Cryptomeria resembles Sequoia , where a group of five or six 
mother-cells are organized (Shaw, ’96, Lawson, ’04). Another striking 
difference between Cryptomeria and Taxodium is that in the latter 
(Coker, ’03) there is a distinct zone of large-celled tissue or tapetum 
surrounding the large spore mother-cell, which persists up to the time 
of endosperm-formation. According to Coker, the function of this large- 
celled tissue is to nourish the young gametophyte. It is therefore regarded 
as a tapetum, which, instead of becoming disorganized upon the germina- 
tion of the megaspore, continues to grow with the developing prothallium, 
and nourishes the latter until the endosperm is fully formed. I was unable 
to find anything that resembled this in Cryptomeria. Surrounding the 
three or four mother-cells, there is present a layer of small elongated cells 
which have the appearance of being crowded by the growing sporogenous 
cells. Soon after the spores are formed these elongated cells become 
disorganized and are probably absorbed by the germinating spore. The 
general appearance of the cells surrounding the megaspore mother-cells 
is shown in Fig. 12 . 
Upon their complete organization the three or four mother-cells 
immediately prepare for division. This is the reduction-division which 
marks the beginning of the female gametophyte. In Pinus (Coulter and 
Chamberlain, ’01), the single mother-cell gives rise to a row of four potential 
megaspores. In Larix europaea (Strasburger, ’79), there are at least 
three potential spores formed from the mother-cell. In Larix Sibirica 
Juel (’00) finds that the first division of the single mother-cell is heterotypic, 
and the number of chromosomes is just half the number present in the 
nuclei of the nucellus. Each of the daughter-nuclei now divides by a homo- 
typic division with the same reduced number of chromosomes. There is 
thus formed from the single mother-cell a row of four megaspores, the 
lowest of which germinates and gives rise to the prothallium. In Sequoia 
(Shaw, ’96, Lawson, ’04) there are five or six mother-cells organized, each 
of which divides twice and gives rise to four potential spores. In Taxodium 
(Coker, ’03) there are two cells formed as a result of the first division 
of the single mother-cell, but only the lower one of these divides again. 
