Affinities of the Palaeozoic Seeds of the Conostoma Group . 29 
cup-like expansion might be regarded as a lateral fusion of a number of 
such major ribs, of which, however, the individuality has been completely lost. 1 
In detail the hard testa was, as in C. oblongum , composed of two kinds 
of elements, viz. an external palisade and an internal fibrous layer ; these 
together attained a width in the middle region of about o*n mm. (palisade 
75 [x and fibrous 38 yot). 
The inner soft portion of the integument is, as in the other species, only 
represented by a micropylar membrane continuous with the plinth jacket, 
and was fused with the nucellus from the base of the plinth downwards ; 
the sinus between the plinth and integument is very clearly seen in J. 3 
(PL III, Fig. 29, s.) } which forms a close parallel to R. no (PI. II, Fig. 14). 
4. The Vascular System . 
The vascular supply further emphasized the differentiation which 
existed between the major and the minor ribs. There were four vascular 
strands, and these occupied the internal angles corresponding to the major 
ribs (PI. Ill, Fig. 27, v.b.) — were embedded in the soft tissue between the hard 
testa and the nucellus. The lowest transverse section (PL III, Fig. 21, v.b)> 
which passes through the base of the megaspore cavity, still shows four 
vascular bundles cut across nearly transversely ; so that if they united it 
was presumably some way down into the stalk. Above, the bundles 
entered the testa at the base of the micropylar cone and passed into the 
tapering loculi of the canopy, which reached to just below the apex (PL III, 
Fig. 29, loci) ; these were no doubt filled, as in the other species, with 
parenchymatous tissue. We see then that the testa here has reached 
a much more advanced stage than in C. oblongum ; the progressive fusion 
of the unit portions of the canopy has gone further, and, corresponding to 
the disappearance of the alternate bundles, their loculi have become com- 
pletely obliterated (PL III, Fig. 23, also Text-fig. 10). 
This differentiation of alternate members in a whorl, of which Conostoma 
anglo-germanicum is so striking an example, finds a close parallel amongst 
modern plants in the ribbed seeds of certain Umbelliferae, where, too, we 
find primary and secondary ridges with vascular bundles situated below 
alternate members. 
There is no evidence for the existence of any soft apical tissue in 
this seed, but the ‘blow-off’ layer -which extended over the whole seed 
attained very considerable dimensions between the major ribs at the apex 
(PL III, Figs. 23 and 29, bli ) ; and radial sections through the minor ribs 
show the cells of this layer with a dimension of as much as 0-19 mm. ; it 
attained, however, its greatest development between the wings at the base 
(PL III, Fig. 21, bL), thus contrasting with the other species in which this 
layer found its minimal development in this region. 
1 F. W. Oliver : On Stephanospermum. Trans. Linn. Soc., 2nd ser., Botany, vol. vi, PI. XLIV. 
