Читать книгу The Circle of Knowledge: A Classified, Simplified, Visualized Book of Answers - Various - Страница 213

It is well-known to every intelligent observer that plants are menaced by a host of enemies. Though the plant cannot take up the aggressive to any extent, the weapons which it employs in its own defense are of an exceedingly efficient nature. In their way they are quite as effective as anything that animals employ in their battle for existence.

Among the commonest defenses of the plant are spines, thorns and prickles. In the sloe (Prunus spinosa), for example, the spines are modified branches; in gorse (Ulex Europæus) they are branches and leaves; and in cacti the green parts are thickened stems and the spines reduced leaves; while in holly (Ilex aquifolium) the prickly leaves answer the purpose of spines. The stinging hairs of the nettle which exude an irritating acid when touched are a familiar example of protection against vegetarian animals.

The way in which seeds are protected by spines is well illustrated in the case of the Sweet Chestnut. Here it would be a very knowing animal that could open one of the cases before they split naturally with the ripening of the seed.