26 BOTANT. 



Practical Studies.— The student should here make a good many 

 ohservatious upon tlie tissues described above, so as to become thoi- 

 oughly familial- with at least their typical forms. The following out- 

 line may direct him in his first studies: 



I. Soft 'lKgsue.—(a) Make very thin cross and longitudinal sections 

 of a green stem of Indian corn. After excluding the woody bundles, 

 the whole of the central part of the stem is soft tissue. 



(J) Make similar secliims of the central part of the stem of the cul- 

 tivated geranium. 



(c) Make a very thin cross-section of an apple-leaf: the green 

 cells are of soft tissue. 



(d) Mount a whole moss leaf: it is entirely composed of soft tissue, 

 although in its rudmieniary midrib the cells have elongated, as if 

 foreshadowing the higher tissues. 



(e) Mount several tlireads of Pond Scum: the whole plant is here 

 composed of soft tissue. 



II. Thick-angled Tissue. — (a) Examine a leaf-stalk of the squash or 

 pumpkin, and note the whitish bands, one or two millimetres wide, 

 which extend from end to end just beneath the epidermis. These are 

 bands of thick-angled tissue. They may be readily torn out, when 

 the stalk will be found to have lost much of its strength. 



(6) Make a very thin cross section of.the preceding leaf-stalk, and 

 note the appearance of the thick-angled tissue first under alow power 

 and then under a higher. The sections must be made exactly at 

 riglit angles to the axis of the bands of tissue in order to. show well. 



(c) Make a number of longitudinal sections of the same leaf-stalk, 

 in each case cutting through a band of the thick-angled tissue. Some 

 of these will show the thickened angles, although there is always some 

 difficulty in making them out in this section. 



(d) Tlie stems of squash, pumpkin. Pigweed or Lamb's Quarters 

 (Ghenopodium), beet, and many other plants may be taken up next, 

 and their thick-angled tissue studied in cross and longitudinal sec- 

 tions. 



III. Stony Tissue. — (a) Break the shell of a hickory-nut, and after 

 smoothing the broken surface cut off a very small thin slice; mount 

 in water and a little potassic hydrate: the cell -walls are so greatly 

 thickened as to almost obliterate the cell-cavity. 



(6) Study similarly the stony tissue of the cocoa-nut, walnut, peach, 

 cherry, etc. 



(c) Make cross-sections of the seed-coat of the apple, squash, meloi 

 wild cucumber (Echinocystis), etc. It is instructive to make sections, 

 also, parallel to the surface of the seeds. 



(d) Make longitudinal sections of the pith of apple-twigs and note 



