288 ESSENTIALS OF BOTANY 



(J) The circle of sheathing leaves at each node. Are the leaves 

 entirely separate from one another ? Split a stem lengthwise through 

 a node and examine it with the magnifying glass. 



(c) The cone at the summit of each stem, composed of .spore- 

 bearing scales. Examine these scales with the magnifying glass to 

 determine their shape. Draw the fertile stem. 



III. Study the sterile stems, noting : 



(a) The position, arrangement, and number of the branches. 



(6) The form of the branches and their resemblances to and 

 differences from the stem. Draw part of a, sterile stem and a 

 slightly magnified branch. 



369. Minute Structure. — Cut thin sections of a fertile and a 

 young sterile shoot between the nodes. ^ Mount in water and ex- 

 amine with l.p. and m.p. Note : 



(a) The general shape of the section. 



(b) The external grooves and ridges. 



(c) The stomata. 



(d) The position of the portions of tissue containing chlorophyll. 

 Is it present in both kinds of stem ? 



(e) The fibro-vascular bundles. 



(/) The air-passages, one in the center and two other sets sur- 

 rounding it. Draw. 



370. The Spore-Leaves. — Using fresh or preserved material, pick 

 off a few spore-leaves from one of the cones. Put them in water in 

 the cavity of a slide with concave center. Examine with the mag- 

 nifying glass, or, if convenient, with a two-inch objective. Note : 



(n) The stalk of the spore-leaf. 



(6) The number and mode of attachment of the sporangia, or 

 cases in which the spores are jjroduced. Draw. 



Tease apart some sporangia in water, mount, and examine with 

 m.p. Note : 



(c) The spores, with attached bands known as elaters. ]Mount in 

 water some fresh spores or those that have been merely dried, ex- 

 amine without a cover-glass, and note the movements of the elaters 

 as the water evaporates. Draw. 



1 Sections of the mature sterile stems are difficult to cut. Prepared slides 

 oJ; tliese and (for comparison) of one of tlie large perennial-stemmed species, 

 as Squisetum hieinale, may be bought of dealers in microscopical material. 



