356 DISTRIBUTION OF BRITISH UMBELLIFER.E 
Gen. 1. Calamites. 
Sect. 1. Aster opJiyllites . — Leaves acicular, one-nerved. 
2. Annularia. — Leaves linear, sometimes obtuse, one- 
nerved. 
3. Sphenopliyllum . — Leaves cuneate, several diclioto- 
mously dividing nerves. 
Suborder II. Equisetece. — Stem herbaceous, articulated, hollow, 
branched ; leaves reduced to a whorl of teeth united by their edges, 
and forming a sheath at the upper end of each articulation ; fruit in 
terminal or lateral strobili composed entirely of peltate fruit-bearing 
leaves, four to seven sporangia dependent from each peltate leaf. 
Gen. 2. Equisetum. 
Obs. As the sections of Calamites agree in the form and structure 
of the fruit, it would be departing from the practice of botanists to 
establish them as separate genera from the diversity which prevails in 
their foliage, however remarkable that may be. 
Explanation of Plate LXX. — Volkmannia Binneti. 
Fig. 1. Spores, showing the liygrometrie elaters. 2. Section of a portion of 
two whorls of leaves, showing the extent to which the leaves of one whorl 
passed beyond the base of the other. 3. An obliquely transverse section, show- 
ing the axis with its central bundle of scalariform tissue, and the apices of the 
leaves of one whorl rising between the leaves of a superior whorl. 4 and 5. The 
cells of the sporangium. 6. An obliquely transverse section, showing several 
sporangia full of spores. 7. Ideal restoration of a single fruit-bearing leaf. 
8. Longitudinal section, showing the apices of some leaves. 9. Transverse 
section, showing six pairs of sporangia. 10. An obliquely transverse section, 
showing the number of leaves in a whorl, the points of the leaves of a lower 
whorl alternating with those of the upper whorl, and the section of one of the 
sporangia bearing disks. 11. An obliquely longitudinal section of the space 
between two leaf-whorls containing the fruits. 12. A longitudinal section of a 
strobilus bent in the middle. 13. An obliquely longitudinal section in which 
the axis is cut away from the lower half, and the transverse sections of the stalks 
of the fruit-bearing leaves are shown in perpendicular series. 14. Longitudinal 
section. 15. Restored transverse section. 16. Restored longitudinal section. 
17. Restored external aspect. 
DISTRIBUTION OP BRITISH UMBELLIFEEiE. 
By W. B. Hemsley, Esq. 
The greater numbers of the genera and species of this family ar 
very limited in area, few Species being common to Europe ami North 
America or to the northern and southern hemispheres; but 37— more 
