VI.] STONEWORTS. 47 



LABORATORY WORK. 



A. NAKED-EYE CHARACTERS. 



Note the slender elongated axis (stem] ; the whorled 

 appendages (leaves') ; the nodes and internodes ; the shortening 

 of the latter towards the apex of the stem ; the rhizoids. 



a. The roots ; small; serving chiefly for attachment, 

 the plant getting most of its nutrition, through 

 other parts, from matters dissolved in the water. 



b. The leaves; their sub-divisions (leaflets)', their 

 form, size, &c. 



c. The spore-fruits and antheridia ; their position, 

 size, form, colour. 



Draw a portion including two or three internodes. 



B. HlSTOLOGICAL STRUCTURE. 



a. The stem. 



1. Examine the outside of a fresh internode with a low 



power, or a pocket-lens, to see the spirally arranged 

 cortical cells. 



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 t set on obliquely round the medullary 

 cell; the nodal cells, and the interruption of the central 

 cavity at the nodes. 



S. 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, 



