276 PLANTS OF NEW ZEALAND 



Older trees of both species have their trunks covered with a 

 light brown bark, that readily strips off, and is frequently 

 used for fire-kindling. For the camper-out, Leptospermum 

 provides fragrant bedding, easily collected, and not readily 

 surpassed for comfort. 



There is little undergrowth in the manuka copse, and the 

 ground below it becomes carpeted with dead leaves, almost as 

 in a pine forest. There are, perhaps, several reasons for this 

 lack of undergrowth. The plant often grows on poor ground ; 

 the resinous leaves may, like the pine needles, make bad 

 mould ; and the shrub itself probably exhausts the soil. Yet 

 sometimes certain orchids are found below it, which are rare 

 elsewhere, and various other plants seem to prefer the manuka 

 grove as a habitat. 



Mr, G. M. Thomson has discussed the probable origin 

 of the New Zealand species. L. scoparium, with sharp 

 leaf tips, is found abundantly in south-eastern Australia ; 

 but L. ericoides, with less pungent points to its leaves, is 

 endemic. Mr. G. M. Thomson states that the rigid, 

 sharp-pointed leaves of the former indicate that the species 

 originated in a land, where there were herbivorous mammalia, 

 for he considers that " such sharp-pointed leaves are 

 probably so developed in order that they may be as 

 obnoxious as possible to grazing animals."" As the genus 

 has come to us from a northern land, where possibly 

 marsupials and other grass-eating animals were abundant, 

 this explanation seems feasible. It also appears to receive 

 confirmation from the fact that the endemic species has 

 less prickly leaf-tips than the one with wider distribution. 

 However, there is another, and, perhaps, simpler interpre- 

 tation of such sharp-pointed leaves. They may be due 

 merely to leaf-reduction, produced as a means of protection 

 against excessive transpiration (v. Aciphylla, Veronica, 

 Discaria). Indeed, that the modification, in the case of 



*New Zealand Journal of Science, Vol. II., p. 371. 



