136 PREPARATION AND MOUNTING 



consists of the discharged spores. This must be carefully col- 

 lected, and should be spread upon the surface of a smoothed 

 fragment of porous sandstone ; the stone being placed in a saucer, 

 the bottom of which is covered with water, and a glass ' tumbler ' 

 being inverted over it, the requisite supply of moisture is insured, 

 and the spores will germinate luxuriantly. Some of the prothallia 

 soon advance beyond the rest ; and at the time when the ad- 

 vanced ones have long since ceased to produce antheridia, and 

 bear abundance of archegonia, those which have remained behind 

 in their growth are beginning to be covered with antheridia. If 

 the crop be now kept with little moisture for several weeks and 

 then suddenly watered, a large number of antheridia and arche- 

 gonia simultaneously open, and in a few hours afterwards the 

 surface of the larger prothallia will be found almost covered with 

 moving antherozoids. Such prothallia as exhibit freshly opened 

 archegonia are now to be held by one lobe between the forefinger 

 and thumb of the left hand, so that the upper surface of the pro- 

 thallium lies upon the thumb ; and the thinnest possible sections 

 are then to be made with a narrow-bladed knife perpendicularly 

 to the surface of the prothallium. Of these sections, which after 

 much practice may be made no more than 1-1 5th of a line of 

 thickness, some will probably lay open the canals of the archego- 

 nia, and within these, when examined with a power of 200 or 300 

 diameters, antherozoids may be occasionally distinguished." 



Another interesting object to the young microscopist is afforded 

 by the spores of the equiseta (or horsetails, as they are often 

 called). These may be obtained by shaking the higher portion of 

 the stems when the spores are ripe. They will then fall like 

 small dust, and may be placed under the microscope. The spores 

 are then seen to consist of a somewhat heart-shaped mass with 

 bands rather intricately curled around it. As they dry these 

 bands expand, and are seen to be four lines at right angles, Avith 

 the ends clubbed, as it may be called. If, whilst watching them, 

 the spores are breathed upon, these bands immediately return to 

 their former state, and are closely curled around the spore ; but 

 as they gradually dry again expand. This experiment may be 

 repeated several times, and is a very interesting one. 



The above are the principal objects which could not possibly be 



