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POPULAU SCIENCE REVIEW. 
elaborate and sensitive tendrils, which seize hold of a stick with 
a rapidity more like the action of an animal than of a plant. 
We shall come hack to this second-class of climbing plants, and 
shall then consider their various kinds of seizing organs. I 
merely wish now to insist on the importance of distinguishing 
between these two methods of climbing, in one of which the plant 
ascends a support hy travelling spirally round it, in the other 
fixes on to the support by seizing it at one place, and continuing 
to seize it higher and higher up as its stem increases in length. 
I have heard the curator of a foreign botanic garden bitterly 
complain of his gardeners that they never could learn the dif- 
ference between these two classes of climbing plants, and that 
they would only give a few bare sticks to some tendril-bearing 
plant, expecting it to twine up them like a hop, while the 
plant really wanted a twiggy branch, up which it might creep, 
seizing a twig with each of its delicate tendrils, as it climbed 
higher and higher. These two kinds of climbers — twiners and 
non-twiners — may be seen growing up their appropriate sup- 
ports in any kitchen- garden where the scarlet-runners twine 
spirally up tall sticks, while the peas clamber up the bushy 
branches stuck in rows in the ground. 
A hop plant will supply a good example of the mode of 
growth of true twining plants. Let us imagine that we have 
a young hop plant growing in a pot ; we will suppose that it 
has no stick to twine up, and that its pot stands in some open 
place where there are no other plants to interfere with it. A 
long thin shoot will grow out, and not being strong enough to 
support itself in the upright position, will bend over to one 
side. So far we have not discovered anything remarkable 
about our hop ; it has sent out a straggling shoot, which has 
behaved, as might be expected, by falling over to one side. 
But now if we watch the hop plant closely, a very remarkable 
thing will be seen to take place. Supposing that we have 
noticed the shoot, when it began to bend over, pointed towards 
the window — say a north window — and that when we next 
look at it after some hours, it points into the room, that is 
to say, south, and again, north after another interval, we shall 
have discovered the curious fact that the hop-plant has a certain 
power of movement by which its shoot may sometimes point in 
one direction, sometimes in another. But this is only half 
the phenomenon, and if we examine closely, we shall find that 
the movement is constant and regular , the stem first pointing 
north, then east, then west, then south, in regular succession, 
so that its tip is constantly travelling round and round like 
the hand of a watch, making on an average, in warm August 
weather, one revolution in two hours. Here, then, is a most 
curious power possessed by the shoots of twining plants, which 
