CHAPTER IV. THE STEM 
I. FORMS AND GROWTH OF STEMS 
Matertau. — Vigorous young hop or bean seedlings grown in pots; 
a fresh dandelion stalk ; a stem of pea, squash, cucumber, grape, or passion 
flower vine, with tendrils. 
AppLiaNces. — A bowl of fresh water; rods of different sizes and 
smoothness for testing the hold of climbers. 
ExprerIMEenT 54. To sHOW THE MOVEMENTS OF TWINING STEMS. — 
Raise a young hop or bean seedling in the schoolroom and allow it to grow 
about two decimeters — 8 to 10 inches — in length before providing it 
with a support. Does the stem form any coils? Bring it in contact 
with a suitable upright support and watch for a day or two. What 
happens? Notice whether it starts to coil from right to left or from left 
to right and see if you can coax it to turn in the opposite direction. When 
it has reached the end of its stake, allow it to grow about five centimeters 
(two inches, approximately) beyond, and watch the revolution of the tip. 
Cut a hole through the center of a piece of cardboard about 14 centi- 
meters (five to six inches) in diameter, slip it over the loose end of the stem, 
and fasten it to the stake in a horizontal position, with a pin. Note the 
position of the stem tip at regular intervals and mark on the cardboard ; 
how long does it take to complete a revolution? Does it continue to coil, 
or to coil as readily, after leaving its stake as before? What would you 
infer from this as to the effect of contact in stimulating it to coil? 
Find out by experiment if it can climb well by means of a glass or other 
smooth rod; by a fine wire; a broomstick; a large, smooth post. See 
whether it does better on a horizontal or an upright support. 
EXPERIMENT 55. To ILLUSTRATE THE COILING OF STEMS. — Run a 
gathering thread in one side of a narrow strip of muslin and notice how 
the ruffle thus drawn will curl into a spiral when allowed to dangle from 
the needle. Can you think of any cause that might act on a stem in the 
same way? Suppose, for instance, that one side should grow faster than 
the other; what would be the effect? (54.) 
Split the stem of a fresh dandelion, or other herbaceous scape, longi- 
tudinally, and immerse it in a pan of fresh water fora few minutes. Notice 
how the two halves curve outward, or even coil up like the strip of muslin. 
This is due to the tension caused by the more rapid absorption of the 
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