B6 



THE YOUNG 



NATUKALIST. 



(i.) those of a general character, pro- 

 tective of the plant as a whole, making 

 it either distasteful or unassailable to 

 any aggressor, such as thorns and 

 prickles, and acrid or poisonous juices, 

 and (ii.) those of a clearly denned local 

 character meant to preserve particular 

 organs, as the spiny leaves which in 

 many plants protect the flowers. To 

 the larger herbivorous or grazing ani- 

 mals, strong, sharp thorns or spines 

 form the most efficient defence, and it 

 is interesting to note the various 

 organs which have been modified to 

 serve this end : in the hawthorn and 

 sloe (Prunns spinosa) the extremities 

 of the branches become sharp-pointed 

 and hardened and so keen as to repel 

 any intruder. Of this character are 

 also the innumerable spines of the 

 furze. It is rather singular that in 

 this plant the seedlings and young 

 root-shoots are so tender and helpless, 

 as it were, being greedily devoured by 

 sheep; but after it has survived the 

 stage of infancy, the mature flower- 

 bearing plant presents an invulnerable 

 front to all assailants. Of a similar 

 structure are the needle -like prickles 

 of the petty -whin (Genista Anglica) 

 and the rest-harrow (Ononis spinosaj. 

 In the barberry and gooseberry the 

 leaves become transformed into the 

 keen-pointed thorns, and it is interest- 

 ing to trace on a twig of barberry 

 the gradual transition from spines to 

 leaves. The common holly is a beauti- 



ful example of a spiny leaf, and the 

 leaves of the sea hollies (Eryngium) 

 are formed on the same plan as are 

 those of the sweet chestnut, whilst 

 the rigid and acicular leaves of the 

 pines and firs bristle like bayonets 

 to guard the plants. In the briars 

 and brambles we have a different organ 

 brought under requisition, for the 

 -prickles of the rose and blackberry are 

 hardened hairs, arising from the 

 epidermis of the plant, as can easily be 

 tested by breaking one off when it is 

 seen to be totally unconnected with 

 the firm woody tissue of the stem. 

 Everyone who has attempted to traverse 

 a thicket of brambles will have a lively 

 appreciation of the aggressive character 

 of their prickles, and no doubt their 

 almost ubiquitous distribution is largely 

 owing to the invulnerable nature of 

 their armour. To this class the spiny 

 prickles of the thistles may be referred, 

 and armed at all points as they are, 

 and furnished with such admirable 

 apparatus for dispersing their seeds 

 it is no wonder they thrive, multiply, 

 and increase. Almost equally effective 

 are the rough prickly leaves of the ox- 

 tongue (Helminthia echioides), a 

 coarse unlovely plant of fields and 

 rubbish heaps, in which each individual 

 prickle arises from a swollen indurated 

 base. Such ponderous weapons may 

 be compared to the ponderous cut and 

 thrust broadsword of the clumsy man- 

 at-arms, whilst the keen slender 



