Cheeseman. — On the Fertilization of the N.Z. Pterostylis. 353 



so strongly marked in Pterostylis, that I have ventured to draw up the 

 following account of my observations on that genus. I have been the more 

 induced to do this from the fact that Mr. Darwin's book '' On the Fertilization 

 of Orchids," which is deservedly considered to be the standard work on the 

 subject, does not contain an account of a similar method of fertilization ; nor 

 is any species described, included in the sub-order Arethusese to which 

 Pterostylis belongs. 



The genus Pterostylis is represented in New Zealand by seven species. 

 Of these, six (P. hanksii, P. graminea, P. rtiicrortiega, P. foliata, P. trullifolia, 

 and P. louherula,) constitute a closely connected series of forms, and seem to 

 present no differences of importance in their fertilization. The seventh species 

 {P. squar}iata) belongs to another section of the genus, and (judging from 

 descriptions) differs in several respects from the others. It is stated in the 

 " Handbook " to have been discovered near Auckland by the late Dr. Sinclair, 

 but I have not been fortunate enough to find it, nor has the plant been seen 

 by any New Zealand botanist of late years. I shall now proceed to describe 

 the mode of fertilization in P. trullifolia, the species on which my observations 

 are the most complete. The accompanying illustration (PI. XX.), containing 

 magnified drawings of the most important parts of the flower, will perhaps 

 cause my meaning to be more easily understood. 



The upper sepal and petals connive and form a kind of hood, inclosing 

 and arching over the column. The lateral sepals are placed in front of this 

 hood, and being united for fully half their length, partially close the entrance 

 to it. The column (see figs. C. and D., and c. in Sg. B.,) is bent backwards at 

 the base, so as to lie close to the upper sepal, with which for some distance it 

 is united; it then becomes erect, and towards the summit is furnished with 

 two broad membranous wings, each of which is extended downwards into a 

 blunt lobe, and upwards into an erect horn-like appendage. The stigma {s. in 

 Figs. C. and D.) isabilobed prominence about the middle of the column. The 

 anther {a., Figs. C. and D.) is terminal, hinged on to the summit of the column, 

 two-celled, the cells opening while the flower is still unexpanded. The pollinia 

 (^., Figs. D. and E.) are four in number, two in each cell, linear in shape. They 

 lie loose in their cells, having no caudicles, and do not become attached to the 

 rostellura. The rostellum (r., in Fig. D.) is an erect, somewhat triangular 

 projection, placed immediately below the anther. Its anterior surface is 

 slightly concave, and consists of a thick mass of highly viscid matter, portions 

 of which can easily be detached. 



The lip, consisting of a linear, somewhat fleshy lamina, with a curious 

 curved appendage at its base, is clawed on to the bottom of the lateral sepals 

 by a delicate ribbon-like membrane. It is extremely sensitive, so that, 

 although in its natural position it has its apex exseited between the free 



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