294 Transactions. — Botany. 



+ 17 cm. in length, with leaflets 65 cm. x 15 mm., or the 

 leaflets may be broader or more narrow. 



When the plant is growing in the open we find a very- 

 different state of affairs. Then very often the leaf-blades 

 are entirely wanting, and the leaf consists only of very long 

 and prickly midribs. Often, however, there is a very small 

 lamina at the apex of tbe midrib (figs. 43, 44, 45), especially 

 in parts of the plant which are most sheltered. Such 

 laminae offer every gradation in size according to their posi- 

 tion with regard to excessive light, wind, &c, between large 

 ones such as described above and those of 2 cm. x 3 mm., or 

 even of much smaller size. On the midribs are many more 

 prickles than on those of the forest liane. These prickles are 

 usually from two to four in number, close together, and situated 

 on the under-surface and sides of the midrib, but never on the 

 stem, each prickle measuring about 2 ram. to 225 mm. in 

 length, and with a stout base 3 mm. or more long. They are 

 of a straw-yellow colour, straight or curved, and so numerous 

 as, with tbeir peculiar colour, to give a distinct character to the 

 plant. 



The plant itself growing in these dry situations — volcanic 

 hills, river-terraces, &c. — forms a round mass of intertwin- 

 ing, long, flexible shoots, having often a height of 61cm., 

 with a diameter of 84 cm., or the dimensions may be very much 

 greater. So elastic is such a bush that when one treads hard 

 down upon it the twigs spring back at once into their former 

 position. This elasticity is exhibited at quite an early age in 

 seedling stems and petioles. From out of the round twiggy 

 mass of the plant erect shoots often arise, quite tender and 

 soft, and with rudimentary leaves. Such are usually killed at 

 a very early stage by the wind and sun. This destruction of 

 the growing -point of the young shoots may account for the 

 non-flowering of the plant, for flower-buds may not develope 

 properly in the dense parts of the twiggy mass, and when 

 exposed to the external climatic conditions are too tender, and 

 so destroyed. In many instances the above-mentioned leaves 

 bend down into the plant for shelter. On this account the 

 lateral leaflets are often bent downwards at an angle to 

 the midrib, which tends to fasten the twigs together, and 

 so to consolidate the whole mass of the plant. 



Several other species of Rubus in New Zealand have the 

 habit of this plant when growing under xerophytic conditions, 

 so assuming the form of shrubs rather than of lianes. Indeed, 

 it is quite easy to see how from such a manner of life, where 

 the climbing habit, suited as it is only for very special con- 

 ditions, is no longer possible, a shrub could be evolved from a 



* " Beitriige z ir Biologie der Lianen," Jena, 1892, pp. 60, 162. 



