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 fibro-vascular bundles, the cavity or canal in 
each, the ring of tissue surrounding the ring of bundles, and the 
Jarger 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 
