OBSERVATIONS FOR YOUNG BOTANISTS 13 
Some of the most remarkable properties of plant life are to 
be seen in the germination of seeds. They are easy of observa- 
tion, and it is the hope of the writer that the following descrip- 
tions will lead the student to make the simple experiments 
herein described himself. 
Structure of Seeds. — To note the different ways seeds 
germinate, it wilt be as well to procure some acorns, cress, beans 
or peas, onion seed, wheat, Indian corn and date stones. They 
are to be sown in flower pots filled with fine moist earth or sand. 
The larger seeds should be well soaked for twenty-four hours or 
more before being placed on the surface of the soil in the pots. 
The parts of a seed consist of the seed skin, which is soon 
ruptured ; within this is the embryo, which begins to grow by 
protruding the radicle, or primary stem, from tlie end of which 
the root is developed. In addition to the embryo there may be 
reserve food-material, or endosperm, as in the four last-mentioned 
seeds. In the first three there is none. 
The Root; Geotropism . — The first thing to notice is that the 
radicle turns downwards. To name this motion the word “ geo- 
tropism,” or “ the turning earth-wards,” has been invented. 
It is supposed to be due to gravity, as seeds at the antipodes 
behave in the same way. If a bean has developed a long radicle 
and it be placed horizontally, .so that the tip is supported by 
a A shaped piece of card, it will be observed after a few hours 
that the tip while growing bends downwards ; but the curvature 
is at a point some little distance from the actual apex. This 
means — as careful experiments have shown — that while the tip 
is sensitive, the “ irritability ” is conveyed up the root to a 
higher point, where the curvature actually takes place. The 
absolute apex consists of a cap of protecting tissue ; but the 
sensitive part is situated just behind it. 
Aphototropism. — This sensitive spot is also affected indirectly 
b}’ light, in that light causes the root to turn away from it,” as 
the above word means, towards the darker side. This may be 
well seen in plants growing near a window which can develop 
roots into the air, as Saxifraga sarmentosa. 
Circiimnutation . — The root, as well indeed, as all parts of 
plants, are constantly moving during growth. It is a kind of 
“ bowing around,” as the above word signifies. It may be 
easily seen in a radicle, when grown as in Darwin’s experiments. 
He took some germinating seeds of horsechestnut and other 
plants. They were placed in a tin box, kept moist internally 
with a sloping bank of clayey sand, on which smoked glass rested 
inclined at an angle of about 65° wdth the horizon. The tips of 
the radicles were placed so as just to rest on the upper end of the 
glass plates, and as they grew downwards they pressed lightly 
on the smoked surfaces and left zigzag or irregular tracks due 
to their movement in trying to circumnutate as a root or stem 
would do if growing freely in the air.* 
This description is taken from Darwin’s “Movements of Plants,” p. 28. 
