Mr. HENDERSON on the Reproductive Organs of Equisetum. 573 
which they occupy; those occupying the muriform and other meshes near 
the inner edge of the theca differ from those on the sides and outer edge; the 
latter are well-defined flattened spiral vessels (Tas. XXXIX. fig. 14. b.) ; the 
former partake more of the character of annular vessels (fig. 14. c.). 
In a portion of the base of the theca near its insertion into the peltate scale, 
the organization is different from any of the above; it consists partly of fibrous 
cellular tissue, something like the inner coating of antheræ, and the outer sur- 
face is formed into sinuous ridges with hollow spaces between. 
EXPLANATION OF THE FIGURES. 
Tas. XXXIX. B. 
Fig. 1. Magnified portion of the theca of Equisetum hyemale, showing the 
rows of muriform meshes on the inner edge, and irregular rows of 
meshes on part of the side. 
Fig. 2. Portion of the theca, showing the outer edge and part of the side, on 
which the meshes are divided into areolz variously inclined. 
Fig. 3. Cells, detached by means of water, when the spores have arrived at the 
globular form. 
Fig. 4. Cells, detached by means of dilute nitric acid, when the spores are in 
the oval state. 
Fig. 5. Granules contained in the fluid of the theca; a.in the early state; 
b. lesser granules, remaining in the mature state. 
Fig. 6. Spore and integument, detached by means of water, immediately after 
the separation of the cells. 
Figg. 7 & 8. Progressive states of the integument, up to that in which the spiral 
sutures are formed. 
Fig. 9. Form of the integument at the time of its separation. 
Fig. 10. Integument, partially separated. 
Fig. 11. End view of the integument, as at fig. 9, showing the transverse 
 sutures, which bound the clavate ends of the filaments. 
4r2 
