558 Saxton.—Contributions to the Life-History of Callitris. 
Several species of Cattitris have been examined from time to time. 
All are so much alike that it may safely be said that the following account 
would apply equally to any of these. That, however, which has been 
mainly studied is Callitris verrucosa , chiefly because it cones freely and 
contains a larger proportion of fertile ovules than most species. In a few 
cases material was fixed in the field, but more usually the cones were 
collected one afternoon, placed in moist packing material and fixed the 
following day, either morning or afternoon. 
The preparations from such material proved quite as satisfactory as 
those from material fixed immediately. 
Description. 
1. The Male Cone. The sporophylls are arranged, like the leaves, in 
alternating whorls of three. Each sporophyll is peltate when mature, but 
when young the proximal part of the blade is curved inwards round the cen¬ 
tral sporangium (PI. XLV, Fig. 1). A single vascular strand passes into each 
sporophyll and terminates a little beyond the large resin cavity. The wall 
of each sporangium (Fig. 2) consists of a single layer of cells ; within this 
are two layers of tapetal cells probably formed by periclinal divisions in the 
sister-cells to those forming the wall. The mature sporangium closely 
resembles that of Widdringtonia , the output of spores being about the 
P.558,1.21. For 500 read 5000 |>, however, from that of Widdringtonia 
in bearing only three (rarely two or four) sporangia (f'ig. 3). 
2. The Female Cone and the Ovide. The young female ‘ cone 5 
consists of six radiating sporophylls in two whorls. Each scale of the 
upper whorl bears about fifteen ovules. The scales of the lower whorl are 
considerably smaller, as a rule, and each bears about five ovules. Thus 
the total number of ovules in a cone is about sixty. The ovules are situated 
on the proximal part of the upper surface and close to the median ridge. 
Ovules prior to pollination have not been seen. The micropyle closing 
cells, like those of Widdringtonia , remain non-septate. The micropyle is 
more widely spreading than in Widdringtonia , as shown in Fig. 4, and its 
wall is either one or two cells wide, whereas that of Widdringtonia is three 
cells wide. A whole ovule in longitudinal section has the structure 
indicated in Fig. 4. (The asymmetric appearance of the section is due to 
it being nearly in the plane of the wings.) 
Pollen tubes may be seen in the nucellus at this stage but have not 
been indicated in the figure. The position of the sporogenous tissue is 
shown. 
3. Megasporogenesis. Only a very small number of megaspore mother- 
cells are found (one to three) and they lie about half-way down the nucellus 
(Fig. 4). Their structure is shown in Fig. 5. They are sharply differen- 
