444 PROTECTION OF (iUEEX LEAVES AGAINST ATTACKS OF ANIMALS. 



long, shiny, brown spines, which often bear flowers; but from the buds on tlie upper 

 half of the shoot, a long axis arises, which repeats the development just desci'ibed. 

 Spines, which on the American species of hawthorn, become in Cratcvr/us coccinea, 

 4 cm., in C. rotundifolia, 6 cm., and in C. Grits galli, 7-8 cm. long, resemble 

 sentinels which have to protect these developing reduced axes. Most of these 

 bushes develop horizontal projecting branches, and therefore extend as far trans- 

 versely as vertically, and since the spines remain for many years, the leaves of 

 all these axes, which, in later years, spring laterally from the branches, almost 

 in the interior of the bush, behind the old spines, are protected by them. In 

 several Brazilian mimosas, the spines situated on the branches do not indeed 

 project beyond the outspread leaves, but as soon as animals disturb the leaves, 

 they are revealed from their concealment behind the protective defence of spines, 

 and the animals retreat before the sharp points now confronting them. 



A very peculiar x-elation is observed between green leaves and spines in 

 most of those semi-shrubs which Theophrastus in olden times grouped together 

 under the name of " Phrygana ". In these semi-shrubs, of which the Vella 

 spinosa, represented in fig. 118', may be selected as an example, each shoot 

 growing out from the winter buds develops green foliage-leaves on the lower 

 half and above these, and frequently also in the region of the inflorescence, 

 green lateral twigs ti'ansformed into sharp-pointed spines. These spines, which, 

 in many instances, as when they appear in tlie region of the inflorescence, may 

 be considered as metamorphosed flower-stalks, are at first soft and succulent, 

 contain green tissue in their cortex, and function at first exactly like the narrow 

 foliage-leaves situated near them. In the first year they play no part as protective 

 agents on account of their softness; in the autumn, the green leaves fall from 

 the shoots; the spinous tips of the bi-anches are also dead and withered, but 

 they still remain, and do not fall off". During the summer, having become hard 

 and stiff", they now wound anyone who seizes them roughly, and obviouslj' protect 

 the shoots which spring from the lateral buds in the following year behind their 

 dried-up ends, in which the development just described is repeated. Thus arise, 

 in time, bristling shrubs, from whose periphery radiate out a quantity of dried-up 

 spiny branches, and which often look as if the branches had become frozen 

 and shrivelled in the winter, and as if the whole plant were in a dying condition. 

 This " Phrygian " underwood is not certainly an embellishment of that region in 

 which it occurs in masses, but it forms a highly characteristic feature in certain 

 floral districts. The Mediterranean area is particularly rich in these " Phiygian " 

 bushes, and sjiecies belonging to the most diverse families develop in this form. 

 To mention only a few examples, of Crucifene, Telia spinosa and Koniga spinosa, 

 of Rosacea3, Poterium spinosuvi, of papilionaceous plants. Genista Hispanica and 

 Onobrychis cornuta, of Compositas, Sonchus cervicornis, of Euphorbiaceae, Eu- 

 phorhia spinosa, of saltworts, Noea spinosissinia, and of Labiatea?, Teucrium 

 svbspinosum and Stachys spinosa, may be pointed out. The elevated stepjies 

 of South-west Asia also exhibit Plirygian forms, and indeed, chiefly, as isolated, 



