406 SECTION-CUTTING 



material) or spirit (for preserved material). Hold the object 

 between the thumb and first finger of the left hand, and arrange 

 the tips of the remaining fingers so as to form a rest on which 

 the razor blade can be glided backwards and forwards through 

 the material. Note that the razor must be gently drawn through 

 the object, and not pressed, as in ordinary cutting. The greatest 

 care should be taken that the axis of the object is either at right- 

 angles (for transverse sections) or parallel to the razor blade 

 (for longitudinal sections). For the latter only a very short 

 length of the stem, etc., should be used. When very thin objects, 

 such as leaves, are to be cut transversely, small rectangular pieces, 

 including a vein, are embedded in a vertical incision made in a 

 short length of Elder-pith. Sections are then cut of the pith, 

 as well as of the embedded object. ' 



After cutting, transfer the sections to a slide, on which a 

 drop of water or dilute glycerine has previously been placed, 

 by means of a well-moistened brush, and reject all but the two 

 thinnest. Complete sections are in most cases quite unessential, 

 whilst the small fragments will usually be the thinnest. Oblique 

 sections, even if thin, are quite valueless. The razor should be 

 carefully cleaned by wiping it from the back towards the edge. 

 IX. The following is an epitome of the main divisions of the 

 Vegetable Kingdom : 

 I. Cryptogamia. 

 I. Thallophyta. 



Flagellata (organisms related to Algae, Fungi, and 

 Protozoa) . 



Bacteria. 



Peridineae (motile organisms of fresh and salt water, 

 possibly related to Diatom aceae). 



Algae. 



(a) Cyanophyceae or Myxophyceae (Blue-green Algae). 



(b) Chlorophyceae (Green Algae). 



(c) Phaeophyceae (Brown Algae). 



(d) Rhodophyceae (Red Algae). 



(e) Diatomaceae or Bacillarieae (Diatoms). 

 Charales (Stoneworts). 



Myxomycetes (Slime Fungi). 

 Fungi, 



