182 Objects for the Microscope. 



The greatest interest of the Sea-weed slides will be lost 

 unless we are acquainted with their fructification ; for no 

 slide is of much value unless it displays either the Tetra- 

 spores, or Favellce, or Ceramidium, or Sori, or Nematliecia, 

 or Antheridia of the various plants. 



It is best to look at these preparations first with the 

 lowest power, a two-inch object glass, which gives a large 

 clear field, and displays the general form to the greatest 

 advantage. Then raise the power successively to examine 

 the fructification, in doing which we may find some beau- 

 tiful specimens of Diatomacese attached to the Algse. In 

 looking over a slide of Ptilota I observed a chain of the 

 frustules of Grammatophora depending- from one of the 

 pinnae, and two or three beautiful Isthmia obliqua entangled 

 in another part of the frond ; some Licmophora were at-, 

 tached to the stem, and this single slide gave long and 

 delightful study, with the use of all the powers of the 

 microscope. 



The fructification of Sea-weed, which is the most im- 

 portant part, can only be understood by-having a collection 

 of about twelve slides, of the following varieties : 



Two slides of Ptilota, which will show either an involucre, 

 containing three spores, or a lacinia, or little leaf, bearing 

 numerous tetraspores, that is, cases containing FOUK spores 

 or seeds. 



Two of Plocamium, which give branches bearing 

 tubercles containing tetraspores, or stichidia containing 

 spores. 



One of Polysiphonia gives an example of a Ceramidium, 

 an elegant urn-shaped capsule, open at the top, and con- 

 taining a group of crimson pear-shaped spores. 



Two of Odonthalia, which has two kinds of fructification ; 

 and on the slide should be either capsular fruit, somewhat 

 like that of Polysiphonia ; or stichidia, long, delicate pod- 

 like receptacles, enclosing crimson spores in separate cham- 

 bers or cells. 



Two of Callithamnion, which has capsules seated along 

 its pinnae, or branchlets with bi-lobed FavelloB. 



Phyllophora shows quite a different kind of fructification, 



