Affinities of the Palaeozoic Seeds of the Cono stoma Group. 7 
2. General Features. 
Conostoma oblongum is a straight, cylindrical, or obscurely prism-shaped 
seed, tapering gently to a blunt point above, where it is perforated by the 
micropyle, whilst below, in the chalazal region, it narrowed more abruptly 
to its insertion on a fairly thick stalk (Text-fig. 3 and PL I, Fig. 1). The 
average length was 5 mm. and the maximum diameter 2-3 mm. The 
seed-base bore six salient ridges, which, running up from the peduncle, 
died out almost at once, reappearing, however, at the apex to form a crown 
around the micropyle. On the main body of the seed these ridges are 
represented by a slight angling of the surface, hardly prominent enough to 
be called ribbing. Perhaps the most interesting feature in the form of this 
Text-fig. 2. Conostoma oblongum. Diagrammatic transverse section of seed cut about i mm. 
below the lagenostome, with plottings of the sections used. References as in Text-fig. i . 
seed is the existence of a slight bilateral symmetry, only trifling in amount, 
but sufficient to rank it technically with the ‘ platysperms ’ (Text-fig. 3, c). 
The internal organization of the seed resembles that of a Lagenostoma 
in so far as the more general relations of integument, nucellus, and pollen- 
chamber are concerned, though it differs from that genus in many important 
particulars. As in Lagenostoma , the single integument or testa is coalescent 
with the nucellus from the seed-base to within about 1-3 mm. of the apex. 
It formed a hard shell to the seed about o*i mm. in thickness, and exhibited 
a very characteristic histological structure. At the summit it undergoes 
marked thickening to form a conical ‘canopy’ surrounding the micropyle. 
