vi.] STONEWORTS. 49 



2. Hold a bit of fresh stem between two pieces of carrot, 

 or imbed it in paraffin, and, with a sharp razor, cut 

 thin transverse and longitudinal slices through nodes 

 and internodes. Note the cavity of the large central 

 cell (medullary or internodal cell) in the internodes ; 

 the cortical cells ; round the medullary cell; the nodal 

 cells, and the interruption of the central cavity at the 

 nodes. 



3. Examine similar sections in specimens treated with 

 spirit, and also preparations made by teasing or press- 

 ing out in glycerine bits of stem from chromic acid 

 (0-2 per cent.) preparations : make out in these, 



a. The nodal, internodal, and cortical cells. 



/3. The wall (sac), protoplasmic layer (primordial 

 utricle), nucleus, and vacuole of each cell. (The 

 nucleus is not always to be found in old cells.) 



4. Examine sections from the fresh stem to make out 

 the points detailed in B. a. 3. (3. The protoplasm 

 and nucleus are difficult to see. Note the chloro- 

 phyll-granules. (See B. b. y.) 



5. Stain sections of the fresh stem with iodine, and 

 magenta: note the results. 



b. The leaves. 



Examine fresh and chromic acid specimens, 



a. The large uncovered terminal cell. 

 (3. Then a series of internodal cells, separated 

 from one another, and covered-in, by nodal 

 cells : the sac, protoplasm, nucleus, and vacuole 

 of each. 



y. The chlorophyll: collected into oval granules, 

 and arranged so as to leave an oblique 

 M, 4 



