402 SPHENOPHYLLALES. A. SPHENOPHYLLEAE 
and position of the sporangiophores, as well as in the number of the 
sporangia borne by each of them. These differences offer curious analogies 
to those of floral construction in Angiosperms: but the latitude of 
variation here shown is such as would in Angiospermic flowers form the 
basis of much wider distinctions than those of species, or even of genera. 
It is not improbable that upon this basis the genus will ultimately be 
broken up, as detailed knowledge of it increases: meanwhile the following 
types of disposition of the sporangia have been described. 
The simplest is that seen in S. ¢richomatosum, Stur, from the Middle 
Coal Measures, where the sporangia appear solitary near to the axils of 
the subtending bracts, which were here of very 
narrow form. It is an open question whether 
Nec: the single sporangium was here really sessile, 
\@) or was borne upon a vascular stalk, as in other 
i. A species, but in this case exceptionally short. The 
| evidence derived from impressions does not suffice 
Bigeiorkt to decide this point (Fig. 218). From the guarded 
Sihevadiyttasi winomatessne statements of Zeiller,? it appears probable that a 
ae ee oe os similar disposition of the sporangia is found also 
(After Kidston.) in S. angustifolium and tenerrimum, and it may 
be noted that these are all small species with 
narrow leaves. In the well-known S. cuneifolium, Stern (S. Dawsoni, 
Will. and Scott), each sporangium, single as in the foregoing species, is 
borne upon an elongated pedicel—the sporangiophore. The sporangio- 
phores in this case are, as a rule, twice as many as the bracts of the 
subtending whorl: each is traversed by a vascular strand which terminates 
at the base of the sporangium. The sporangiophores are inserted close to 
the base of the leaf-verticil, which is here webbed into a wide cup: and 
to this the pedicels mvay be adherent for varying distances upwards (Fig. 
219). The vascular supply of the sporangiophores is derived by branching 
from that of the subtending bract, of which they thus seem to be 
appendages. In the regular cases the foliar strand on entering the verticil 
divides into three, the single lower branch supplies the bract, while the 
other two enter the two sporangiophores.? A further complication is seen 
in S. &émert, Solms Laubach, for in this cone two sporangia are borne 
on each sporangiophore, hanging down from its peltate distal end. The 
sporangiophores are disposed in three concentric verticils on each whorl of 
bracts, and are attached by short stalks traversed by a vascular strand, 
which branches to supply the two sporangia (Fig. 220). The analogy with 
the sporangiophore of the Equisetales is more obyious here than in the 
previous cases, where only a single sporangium is borne on each. But it 
appears still more plainly in S. majus, Brongn., from the Middle Coal 
Measures, but as yet known only from impressions. This species 1s 
LL’ Appareil Fruct. d. Sphenophyllum, pp. 31, 32. 
?For details, see Scott, Studies, p. 93, etc. 
