PROTECTION OF GREEN LEAVES AGAINST ATTACKS OF ANIMALS. 443 



Mullein to the mucous membrane rests the necessity for the caution which 

 people observe in the preparation of Mullein. The flowers of the Mull.in 

 (Verbascum thapsus) have been used from time immemorial in the preparation 

 of a tea. When hot water is poured over the flowers, which are covered on 

 the under side, just like the foliage-leaves, with a fine felt of hair, portions 

 of the felt are detached, and remain floating in the infusion. If the decoction 

 is not filtered through a piece of linen, some of the hairs may stick to the mucous 

 membrane of the mouth, and there produce an intolerable irritation and itching. 

 This unpleasant sensation is certainly much more powerful in animals when 

 taking the leaves of Mullein in their mouths than with us when we drink 

 unfiltered mullein tea, and it no doubt deters animals from eating the foliage of 

 the plants in question. 



The protective mechanisms just described are all borne directly by the par- 

 ticular organs needing protection. But there are many plants whose foliage is 

 unequipped with armament of this sort, and in which adjacent parts of the plants 

 afford the protection. One may instance all such plants as have soft, unarmed 

 leaves, sheltered from attack by lateral shoots transformed into spines. The stem 

 and branches of these plants are not clad with foliage entirely to their summits. 

 The ends are usually leafless, and look as if their leaves had been stripped off*. 

 Generally speaking, if leaves are present on the summits of the branches, they 

 are stunted, small, indicated only by scales and protuberances, and are anything 

 but an attractive food. Consequently, the end of the woody branch appears 

 tapering, and terminates in a stiff, sharp spine. In a bush whose branches project 

 out in all directions with leafless apices, while their green foliage -leaves are 

 collected behind the apex, a most efficient system of defence is produced, resting 

 upon division of labour. The green leaves can carry on the work assigned to 

 them undisturbed under the protection of the spines, and if it happens now 

 and then that a large food-seeking animal, driven perhaps by greed or hunger, 

 pushes his mouth carefully between the confronting spines, and knows how to 

 procure some green leaves from behind the spines, the existence of such a bush 

 is not seriously threatened. The Alhagi shrubs of steppes, as well as several 

 brooms and Cytisus shrubs, viz. Alhagi Kirgisorum, Genista horrida, and Cytisus 

 spinosus (fig. 118 5 ), exhibit the protective mechanisms just described in a marked 

 manner. In many other shrubs, such as sloes, sea buckthorns, and buckthorns 

 (Prunus spinosa, Hippophae rhamnoides, Rhamnus saxatUia), the same con- 

 trivance is indeed met with, but it only has the full significance while the foliage- 

 leaves are quite young. Only so long as the tender leaves, which have just emerged 

 from the buds, are overtopped by the spiny branches are they protected from being 

 devoured; afterwards when they have developed, those only are protected which 

 clothe the base of the spiny branches. On the long axes of the Hawthorn, in 

 the axils of the lower foliage-leaves, there are always developed, close together, 

 a lung spine and a small bud, in the axils of the upper leaves a bud only. In 

 the following year, reduced axes develop from the buds situated close to the 



