18 
A. E. GIBBS—SEEBS AND ERTJITS J 
mentioned above. When the seed germinates in the ground the 
young stem always grows towards the sun, and this is through the 
action of another force called heliotropism, or an attraction towards 
the light. The slightest ray is sufficient to direct it through the 
smallest fissure. Tor instance, if a plant be grown in a dark place 
and a ray of light is thrown down a metal tube, so sensitive is the 
young stem that it will grow towards that light. 
Let us now turn to the consideration of the different kinds of 
seeds and fruits. A moment’s reflection will show how greatly 
they vary in shape, size, colour, taste, and in many other ways, and 
we shall see that there are good reasons for all these differences. 
Many seeds require protection and are enclosed in a hard covering, 
and we have a good example of this in the cocoa-nut. There the 
embryo is almost impregnably fortified by double armour. JSTot 
only is there a hard shell, but outside that there is also a thick cover¬ 
ing of fibre, from which cocoa-nut matting is made. As the cocoa- 
nut is often exposed for a great length of time to sea-water, and 
tossed about by currents and drifted from one island to another, we 
see how necessary these coatings are for its protection. Many nuts 
are found strongly protected, especially such as are a favourite food 
of animals. The poisonous qualities of some fruits have protective 
functions. Other fruits seem to be protected by the bitter taste 
of their husks. Many fruits, such as the plum and cherry, which 
when ripe are edible and luscious, before they come to maturity 
are sour and unpalatable, but when they begin to approach 
maturity and the period arrives for the seeds to be set free, a 
chemical change is set up, the acids disappear, and sugar is formed, 
making the fruit tempting to the palate of animals. Then in some 
plants peculiar movements take place in order that the unripe seed 
may be protected, and we see a very curious example of this in the 
common dandelion. The flower-head is situated on a long foot¬ 
stalk, which, when the flower comes out, stands straight up so that 
the blossom may be seen by passing insects which perform the 
necessary offices of fertilization. It remains in that position three 
or four days. When fertilization has taken place the flower-stalk 
bends over until the flower-head lies upon the ground and is hidden 
among the leaves, and there it remains maturing its seed for about 
twelve days, but as soon as the seed is set the flower-stalk erects 
itself again that the ripened seed may be carried away by the wind 
and dispersed. In the cyclamen, after the flower has faded, the 
stalk curls itself up into a beautiful spiral. The coltsfoot (Tussilago 
Farfara) also inverts its capitulum while the fruit is ripening. 
Take another instance. The familiar little Linaria Cymbalaria , so 
common on old walls, exhibits a similar set of movements. When 
the blossom comes out the flower stands up, but after fertilization 
the foot-stalk bends round and hides among the foliage or in some 
hole in the wall until the seed is ripe. In plants that grow in the 
water, the same end is often attained by the flowers rising to the 
surface for the seed to be set and then sinking into the water again 
for it to ripen. This is the case with the water-lilies and some 
