570 Mr. Henderson on the Reproductive Organs o/Equisetum. 



water, they are found to consist exclusively of the lesser granules, the larger 

 ones having now altogether disappeared. As the spore swells, the divisions of 

 the integument are forced asunder ; a portion at each end however generally 

 adheres longer, and preserves the form represented at Tab. XXXIX. fig. 10.; 

 and although further separated, these divisions are still held in their spiral 

 position until the ripening of the spore, when, being ejected from the theca, 

 they recoil with a jerk, and immediately twist into narrow clavate filaments, 

 the state in which they have been most frequently observed. Tab. XXXIX. 

 fig, 12. represents the spore previous to its ripening and to the opening of the 

 theca; the filaments are partly unrolled, and their attachment to the spore 

 and to each other is shown. 



In the ripened state the spore has a wrinkled or plaited appearance, arising 

 from some peculiarity in its immediate covering, which appears to add greatly 

 to its opacity. On the application of water to the spore, it immediately swells 

 to considerably beyond its original size, the wrinkles on its surface disappear, 

 and it changes to a bright green colour. By adding tincture of iodine to 

 the water a very curious effect is produced, which proves the existence of an 

 outer and inner membrane or tunic to the spore : its nucleus is contracted 

 to a much smaller size, leaving the outer membrane occupying the space to 

 which it had been distended by the water, and appearing under transmitted 

 light like a transparent limb to the opake spore (Tab. XXXIX. fig. 13.). The 

 spore on arriving at maturity acquires a dark green colour ; it contains a thick 

 viscid fluid, copiously mixed with minute granules exactly similar to those 

 contained in the pollen-grains of flowering plants ; they seem not to differ 

 greatly from, if they are not identical with, the lesser granules found in the 

 integument and in the intercellular cavities of the theca. The larger granules 

 having all disappeared immediately after the separation of the integument, it 

 would appear that their functions are somewhat different from those of the 

 lesser ones ; the former, I have no doubt, are of an amylaceous nature, being 

 soluble in boiling water, but not in alcohol. I inclosed some spikes of Equi- 

 setum hyemale, in that state when the granules of both kinds are most nume- 

 rous, in a phial with water ; the phial was then held in a vessel of boiling 

 water for half an hour, and on examining the thecse, I found that the larger 

 granules had all disappeared, but that the lesser ones remained unaltered. 



