356 Transactions.— Botany. 
insect has been modified to suit the relative size of the species by which the 
plant is fertilized, for if the passage had been of a size sufficient to allow the 
largest individuals to escape with ease the smaller ones would perhaps have 
been able to pass through without touching the rostellum, and consequently 
would not remove the pollinia. 
It seldom happens that all the pollinia are removed. Out of 110 withered 
flowers twenty-eight had all the pollinia remaining in their anther cells, 
twenty-nine had lost one, thirty-four two, thirteen had three withdrawn, while 
only six had all four removed. Seventy-one of the flowers were fertilized, but 
it must not be forgotten that a large number of the unfertilized ones drop off 
before commencing to wither, so that the proportion fertilized is really much 
less than this, Probably not one quarter of the flowers ever produce 
capsules. 
Of the other species of Péerostylis, P. banksii, P. graminea, and P. 
puberula are fertilized in exactly the same manner. There are, of course, 
slight differences in the size and arrangement of the parts of the flower, but it 
is hardly worth while describing these in detail here. In P. puberula nectar 
appears to be often present on the outside of the lateral sepals, near the point 
of their coalescence, serving, no doubt, to attract insects to the flower. 
P. banksii also has two minute papille at the base of the column, which may 
secrete nectar, but I have never observed any. The insect which fertilizes 
this species is nearly twice the size of that which performs the same office for 
P. trullifolia. I have seen an insect enter the flower of P. graminea and 
become entrapped by the lip. With P. micromega I am imperfectly acquainted, 
but believe the fertilization to be on the same plan. Of P. foliata I have only 
seen dried specimens, but as the structure of the flower is in the main the 
same as in P. trullifolia I have no doubt that it-will prove to be fertilized in a 
similar way. 
It seems hardly necessary to draw attention to the fact that the elaborate 
structure displayed in this genus is solely used to insure the pollen of one 
flower being placed on the stigma of a different one. It is not too much to 
say that the pollinia can never reach the stigma of the same flower, except, 
perhaps, by a combination of circumstances extremely unlikely to happen. 
As all our New Zealand species have solitary flowers, the cross effected is not 
only between different flowers but between different plants. 
DESCRIPTION or PLATE XX. 
Pterostylis trullifolia, Hook: f. Natural size. 
A. Front view of flower. 
. B. Lateral view of flower. The sepals and petals on one side removed to 
Bos the position of the column and lip. 
