82 
L. Cockayne. 
Also, so high an authority as Goebel does not consider Lothclier’s 1 
experiments with regard to the suppression of thorns and prickles 
by moist air culture as conclusive, since he writes 2 :—“ 1 do not 
think that up till now any more has been proved than that in moist 
air the formation of prickles and thorns is retarded, there is no 
proof that it can be suppressed.” I do not know, since botanical 
literature is not abundant in this distant land, whether fresh facts 
throwing light on this subject have been published since Goebel 
wrote the above. It however seems to me, that my experiment 
detailed above is a fairly crucial case, and that in Discarin 
Toumatou, at any rate, the spines are a direct response 3 to conditions 
of dryness, and function as a special “ contrivance ” for checking 
transpiration. If so, then they have nothing to do primarily with 
attacks of grazing animals, especially when it is borne in mind 
that New Zealand never contained such, excepting the various 
species of Moa. With regard to the effect of these giant birds on 
New Zealand Plants, it may be pointed out that, as they probably 
fed upon certain shrubs, protective adaptations might be expected 
in such. On this head, some observations of G. M. Thomson are 
of interest. In a paper dealing with the origin of the New Zealand 
flora, 4 he pointed out that plants with spines or prickles are 
extremely rare in New Zealand, while such, when they occur, are 
not usually endemic but rather species identical with or closely 
allied to those of lands where grazing animals are frequent. 
Certain species of Aciphylla, a palaeoceanic genus, form a striking 
exception to the above, as Thomson also remarks. Wallace is of 
opinion 5 that these “ may have gained their spines to preserve them 
from being trodden down or eaten by the Moas.” But in this case, 
there is distinct evidence to the contrary, for, as I specially noted 
when studying the plant-formations of the Waimakariri tableland, 
that most bayonet-like of plants, Aciphylla Colensoi, had its inflor- 
1 Recherches sur les plantcs a piquants. Rev. gen. de bot. T.V., 
1893. 
2 Organography. (Eng. Trans.) Pt. I., 1900., pp. 203, 264. 
3 I do not mean by this that dry air is the sole cause of spines 
being developed, but that it acts as a stimulus in calling forth 
a certain innate tendency in the plant, which at the same time 
has an equally great tendency to produce leafy shoots, and 
will do so on being subjected to the appropriate stimulus. 
How powerful this latter tendency is, is shown by the fact 
that the Discaria in spring frequently produces true reversion- 
shoots. 
“ Trans. N Z. Inst. Vol. XIV, 1S82, pp. 496-7. 
6 “ Darwinism.” p. 433. 
