294 FOUNDATIONS OF BOTANY 



361. Sterile Stems. Examine the stems above ground with 

 reference to their color and mode and degree of branching. What 

 is the character of the leaves ? Do the stems in any sense serve as 

 leaves? Observe the nodes composing the stem and note the posi- 

 tion of the leaves on the stems. Do they appear to be placed several 

 at the same level (whorled) ? 



Examine with a magnifying glass the surface of the stem and 

 note the number of ridges and grooves. Compare the number and 

 position of the leaves with reference to these. 



362. Mineral Matter in Stem. Treat small pieces of the stem 

 with strong nitric acid to remove all vegetable substance and note 

 the mineral substance remaining. Treat in a similar way thin cross- 

 sections and examine under the microscope. The substance is 

 silica. It gives the plant its gritty feeling and its name and use as 

 " scouring-rush." Of what use is it to the plant? Use of the same 

 substance in outer rind of corn stem, bamboo stem, and straw of 

 grains ? 



363. Microscopic Examination. Make thin cross-sections of the 

 stem and examine under the lowest power of the microscope. Make 

 a diagrammatic sketch to indicate the central cavity, the number 

 and position of the nbro-vascular bundles, the cavity or canal in 

 each, the ring of tissue surrounding the ring of bundles, and the 

 larger cavities or canals outside of this. Where is the chlorophyll 

 located? Can stomata be found, and if so, what is their location 

 and arrangement? 



364. Fertile Stems. Describe the fruiting stem with reference to 

 general aspect, size, color, number, and length of internodes, position 

 of spore-bearing portion, color of spores in mass. Note the shield- 

 shaped bodies (transformed leaves or sporophylls} composing the 

 cone-like "flower" and see whether any joints can be detected where 

 they are attached. Examine the inner surface of the shields for 

 sporangia and spores. Examine the sporangia under a low power 

 of the microscope. Examine some spores under a higher power. 

 Note the two bands, elaters, on each spore, crossing each other and 

 attached only at the point of crossing, forming four loose appendages. 

 Watch these while some one moistens them by gently breathing 

 upon them as they lie uncovered on the slide under the microscope 



