Cheeseman. — On the Fertilisation of 



319 



Art. L. — On the Fertilisation of Acianthus and Cyrtostilis. 



By Thomas F. Cheeseman, E.L.S. 



[Read before the Auckland Institute, 1st June, 1874] 



1. Acianthus sinclairii. 



find 



so remarkable and unique as those that obtain in Pterostylis, or in other of 

 the New Zealand Orchids ; on the contrary, the mode employed is simple, and 

 presents few features of interest. Yet, if the completeness of any method of 

 fertilisation is to be judged of by the results obtained, as undoubtedly it 

 should be, we must regard that of Acianthus as one of the most perfect of the 

 many different modes in use among our Orchids. 



The flowers, varying in number from one to twelve, are minute, and of an 

 inconspicuous appearance. The lip, which is horizontally spread out in front 

 of the flower, or slightly deflexed, is ovate-lanceolate in outline, and greatly 

 concave, so as to form a kind of bucket. At its base it is furnished with two 

 large glands, and the margins and point are also plentifully studded with 

 minute fleshy papillae. The column is somewhat curiously shaped. At first it 

 is erect, but towards the summit suddenly arches over the lip, and is much 

 thickened and expanded. The anther is terminal, two-celled, each cell 

 possessing two pollinia, which are deeply bilobed, so as to resemble a horse 

 shoe in shape. The stigma is a deep circular hollow situated just below the 

 anther ; and, by the arching of the upper part of the column, hangs directly 

 over the lip. The rostellum is placed on its upper margin. It consists of two 

 triangular projections, which at first are cellular, but ultimately resolve into 

 masses of viscid matter, covered with an extremely delicate membrane. As 

 the flower expands, the connection of these projections with the rest of the 



can 



stigmatic 



quite plane. 



Long before the flower opens, each lobe of the anther splits gradually from 



una 



the rostellate points. The pollinia then emit a number of excessively delicate 



become 



to it. So that, in a fully expanded flower, each set of pollen-masses is quite 

 free from its anther cells, but they are firmly attached by their bases to their 

 respective rostella, neither of which can be removed without bringing away 

 the pollinia. 



glands 



them. From this circumstance alone we might surmise 



