SPERMATOPHYTES 
205 
bears one or two bractlets and a terminal ovule (fig. 463). The bearing 
of ovules on secondary axes of the strobilus results in what is called a 
compound strobilus, a type of strobilus characteristic of certain conifers. 
Ovules. Although the 
structure of the testa is not 
clear in the sections that have 
been made (fig. 463), two 
layers are evident (the outer 
fleshy and the stony), and it 
is probable that an inner 
fleshy layer was also present. 
This type of testa is char- 
acteristic of the whole cycad 
line of gymnosperms. An- 
other primitive feature of the 
ovule is that the nucellus is 
quite free from the integu- 
ment, and that one of the 
sets of vascular strands trav- 
erses the outer fleshy layer, 
and the other set traverses 
the peripheral region of the 
nucellus. This structure is 
duplicated only among the 
Cycadofilicales. There is also 
a prominent nucellar beak 
and a large pollen chamber, a 
structure which indicates the 
existence of swimming sperms. 
FIG. 462. Section of staminate strobilus of 
one of the Cordaitales, showing the spirally ar- 
ranged sterile bracts, and the stalked stamens 
bearing terminal sporangia (the longitudinal de- 
hiscence of the sporangia not shown). After 
RENAULT. 
Male gametophyte. The 
pollen grains are preserved in 
abundance, and in favorable 
specimens a group of internal 
cells is evident (fig. 464), 
which must represent a male gametophyte; but whether these cells are 
vegetative or spermatogenous or both cannot be determined. In either 
case, the number of cells indicates a very primitive condition. 
Female gametophyte. The female gametophytes resemble those of 
modern gymnosperms. Two archegonia have been seen, and between 
