568 Mr. Henderson on the Reproductive Organs o/'Equisetuni. 



from time to time on Equisetinn Jii/emah and other species) I shall endeavour 

 to show that the filaments attached to the spores of Eqitisetiim are separated 

 portions of an oval integument which envelopes the spore in its early state, 

 and which, being attached to it on one side, and opening by spiral sutures or 

 slits as the spore approaches to maturity, finally on its escape from the theca 

 unrolls, and separates into two filaments with clavate tips attached by their 

 middle to the spore. When the spike or fructification of Equisetum hyemule 

 first begins to swell beyond the terminal sheath, the spores may be observed 

 in a rudimentary state on carefully dissecting the theca, the interior of which 

 is at this time divided into cells of extreme tenuity, in which the spores 

 originate. These cells are filled with a viscid, greenish-coloured fluid, which, 

 when mixed with a small portion of water and highly magnified, will be found 

 to contain innumerable minute granules, possessing spontaneous motion, and 

 moving apparently on tlieir axes with considerable rapidity : they are of various 

 sizes (fig. 5.) and of various shapes, the larger generally oblong, the lesser sphe- 

 rical : they are all equally active, and being transparent, they communicate a 

 whitish colour to the water when viewed with the naked eye. 



Tab. XXXIX. fig. 3. represents four cells detached by means of water, con- 

 taining the spores in the position which they occupy within the cells ; at first 

 their form is oval or ovate, but they very soon change to globular, the form 

 which they afterwards retain. It is extremely difficult at this time to detach 

 any of these cells entire, owing to the filmy condition of their walls and the 

 viscid nature of their contained fluid : a better opportunity is afforded of view- 

 ing their form and arrangement by macerating the theca in dilute nitric acid, 

 when they appear somewhat shrunk and collapsed, and the minute granules 

 are therefore easily discerniijle in the cells (Tab. XXXIX. fig. 4.) and also in 

 the spores : the whole mass is easily forced asunder even to the theca, which 

 separates into parts corresponding with the sides of the outer cells. Consider 

 able changes take place in the spores from the state here noticed in their 

 progress to maturity; these are accompanied by other and very remarkable 

 changes in the theca as well as in the cells. These latter gradually acquire 

 substance, separate from each other, and, changing their form, become first 

 globular, and afterwards oval integuments of the spores ; the spaces caused by 

 their separation being filled up with a dark green viscid fluid containing 



