kidston: the flora of the carboniferous period. 361 
Fig. 13. — Sphenophyllum 
majiis Bronn. Bract 
showing four sporangia 
— sessile and united to 
each other by their 
bases. 
The fructification, often placed on short lateral branches, is 
commonly in the form of terminal cones composed of more or less 
modified leaves whose basal portions unite to form a saucer-like 
collar surrounding the axis. The distal portion of the bract is free 
and erect. In the cones the whorls of bracts alternate, but on 
the stems the leaves are superposed. 
In Sphenophyllum majus Bronn. sp. 
the fruiting portion of the plant is little 
modified from an ordinary foliage branch, 
though the bracts are united into a very 
narrow collar which surrounds the stem. 
Fig. 13. 
The arrangement of the sporangia 
in the cones of the various species varies 
considerably. 
In Sphenophyllum cuneifolium, the common Middle and Lower 
Coal Measure species, the sporangia usually form three whorls placed 
on pedicels of varying length which, however, all spring from the 
bract close to the axis. Text Fig. 14. It therefore follows that those 
of the first whorl have shorter pedicels than those of the second, while 
those of the third whorl have pedicels 
longer than those of the two inner circles 
of sporangia. A small vascular bundle 
enters each pedicel or sporangiophore, 
which is therefore most probably a modi- 
fied segment of the bract. 
In Sphenophyllum trichomatosuin 
Stur the sporangia are sessile, Fig. 15. 
In Sphenophyllum majus Bronn. sp. the 
sporangia are also sessile, but united by 
their bases into groups of four, Fig. 13. 
The spores of Sphenophyllum are very characteristic, the spore 
membrane being ornamented with spine-like projections connected 
by a series of reticulate ridges. 
The stem of Sphenophyllum consists of a solid axis, formed of 
a primary, three-rayed, vascular star, developed centripetally. To 
I^g. 14. — Sphenophyllum 
cuneifolium Sternb. sp. 
Arrangement of the 
sporangia. 
