543 
Dull —Pity ostrohus macrocephalus , L. and H. 
collection of three or more grains, but the outlines are so indistinct that 
it is hardly possible to say whether a wing is present or not (see Fig. 15, 
PL XV), 
No other examples have been found in any other ovule. Some much 
smaller spherical bodies, with a thin wall and filled with contents, have been 
observed in the neighbourhood of the nucellar apex ; these seem to repre- 
sent some sort of fungal spore. The nucellar apex often appears to have 
been perforated by pollen-tubes (this is evident in Fig. 15, PL XV), and 
a possible example of the invasion of the prothallus by a pollen-tube has 
been mentioned already. 
Theoretical Considerations. 
Before proceeding to discuss the significance of the special features 
associated with the cones just described, it will be as well to consider briefly 
the grounds on which it may be inferred that we are dealing with a single 
species only. The two species to which all the present material has been 
referred were founded entirely on differences in external appearances. 
Carruthers mentions only differences with respect to the form of the cone 
and the shape of the apophyses. His diagnoses read : 
1. Pinites macrocephalus . Cone cylindrical, obtuse at both ends ; scales 
with thick and flat, irregularly six-sided apophyses ; basal scales largest. 
2. Pinites ovatus. Cone ovate, with a truncate base and obtuse 
apex ; scales with thickened, flat, sub-quadrangular apophyses ; basal scales 
largest. 
He states in his description of Pinites ovatus that this cone can be 
readily distinguished from that of P. macrocephalus ‘ by the form of the 
apophyses of the scales, which are longer than they are broad, and quad- 
rangular or sub-quadrangular, the upper and lower angles being acute or but 
slightly truncate As to the general validity of this I am unable to judge, 
but some doubt has already been thrown on the value of this criterion 
in view of the intermediate character of the apophyses of the Sedgwick 
Museum cone. 
A conspicuous difference in the appearance of the slides examined 
is to be found in the darker colour of those of P. macrocephalus . This 
is particularly noticeable in the Cowderoy specimens. It is partly due tc 
the greater thickness of the sections* but largely also to their siliceous 
matrix being actually darker and containing a larger proportion of black 
carbonaceous matter. In all cases, however, the actual tissues preserved are 
exceedingly alike in form, structure, and arrangement. In both forms the 
scales possess the same general shape, with a nearly horizontal proximal 
portion, and, according to Carruthers, both possess the long basal scales 
which form so distinctive a feature of these cones. Another characteristic 
