CHAPTER II. PLANT TISSUES. I 73 



glass ; gently tap the latter with a needle-point, so as to jar the cells apart, and 

 study the prosenchyma tissues. 



Wood-cells, tracheids, bast-cells and spiral, annular and reticulate ducts 

 may readily be distinguished. More satisfactory results will be obtained if, 

 after treating the section with Schulze's maceration fluid and washing, it be 

 stained with an aqueous solution of methyl-green. The liquified tissues will 

 then be more strongly stained than the rest and their structure more readily 

 recognized. Make drawings of each of the tissues. 



With a very sharp plane, make of White Pine wood thin cross-sections, thin 

 longitudinal sections parallel with the rings of growth, and thin longitudinal 

 sections at right angles to the rings of growth, and study the discigerous tra- 

 cheids. Make drawings of them as they appear in the different sections. 



With a sharp knife, make some thin sections of the shell of a Hickory nut, 

 some of them parallel with the surface, and others at right angles to it; treat 

 the sections with hot Schulze's maceration fluid ; rinse, stain with methyl- 

 green, mount in water, and jar the cells apart by tapping the cover-glass with 

 a needle ; then study the cells with a magnifying power of 300 or 400 diameters. 

 Observe the excessively thickened walls, and the concentric and radial markings, 

 and make drawings illustrating the shape and structure of the cells. 



Make transverse and longitudinal sections of the stem of the Yellow Dock, 

 Rumex crispus, and examine them for collenchyma tissue. In the transverse 

 section this will be observed in masses in the obtuse angles just beneath the 

 epidermis. It should be studied under a magnifying power of 400 or 500 diam- 

 eters. Draw a portion of the tissue as it appears in both sections. 



Excellent examples of this tissue are also found in the petioles of the Pie- 

 plant, Begonia, and Grape. 



Beautiful examples of scalariform ducts may be isolated for study by treating 

 longitudinal sections of the underground stem of the Common Brake, Pteris 

 aquilina, with Schulze's Maceration fluid, and fine examples of dotted ducts 

 may be found in many common woods, as the Maple, Walnut, Oak, Butternut, 

 etc. Trabecular tracheids may be found in the leaves of the common Juniper. 



For the study of sieve-tissue, transverse and longitudinal sections of the 

 stem of the Pumpkin may be made. In the transverse section they appear as 

 rather large cells in the outer and inner portions of the radially elongated 

 fibro-vascular bundles. The longitudinal sections are best studied by treating 

 them first with alcohol, to kill the protoplasm, and then, after rinsing in water, 

 staining them with eosin. The proteid contents of the sieve-tubes will then be 

 shrunken and stained bright red, so that the tubes may readily be traced. 

 This treatment is not advantageous for the cross-section, as the staining of the 

 albuminoid matters in the cells obscures the sieve-plates. The latter may be 

 rendered beautifully distinct by soaking the section in a solution of soda-corallin. 

 This serves well also for the study of the longitudinal section. Draw one or 

 two of the sieve-tubes. They may also easily be studied in the petiole of the 

 Grape. 



Simple laticiferous tissue may be studied in the stem of Euphorbia splen- 

 dens, or in that of other species of Euphorbia. The stem should, immediately 

 after removing it from the plant, be placed in strong alcohol, to coagulate the 



