XIV.] STONEWORTS. 437 



2. Hold a bit of fresh stem between two pieces of elder- 

 pith 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 internodal cell ; the cortical cells, round the 

 internodal 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 

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



a. The nodal, internodal, and cortical cells. 



/?. The wall, protoplasmic layer {primordial 

 utricle), nucleus, and vacuole of each cell. 

 (The nucleus will have undergone fragmenta- 

 tion in the older cells.) 



4. Examine sections from the fresh stem to make out 

 the points detailed in B. a. 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 with 

 magenta : note the results. 



b. The leaves. 

 Examine fresh and chromic acid specimens, 

 a. The large uncovered terminal cell. 

 /?. Then a series of internodal cells, separated 

 from one another, and covered-in, by nodal 

 cells : the cell-wall, protoplasm, nucleus, and 

 vacuole of each, 

 •y. The oval chlorophyll-granules, arranged so as 

 to leave an oblique uncoloured band round 



