292 Transactions. — Botany. 



two or three cases of self-fertilization given by Mr, Darwin himself, several 

 other instances have since been added, but even then the total number is 

 small, and bears no sensible proportion to the overwhelming majority de- 

 pending on cross-fertilization for the production of seed. 



Some of the most interesting exceptions to the rule yet recorded occur in 

 the Australian and New Zealand genus Thehjmitra. The Australian species 

 have been ably investigated by Mr. Fitzgerald, who finds in the genus almost 

 all the links between forms that are utterly sterile and barren without insect 

 aid, and others that are regularly self-fertilized from one generation to 

 another, and in which the flowers have almost become cleistogene. As 

 nothing has been pubhshed about the New Zealand species, I propose to 

 give a sketch of the fertilization of one of them — T. longifolia, pointing out 

 some apparent differences between the method employed here and that which 

 according to Mr. Fitzgerald is in use in Australia. 



Thehjmitra longifolia is probably the most abundant Orchid in the North 

 Island, Its favourite station is on clay hills, but it can also be found in dry 

 rocky places, on sand-hills, and even in wet swamps ; in short, in all soils 

 and situations, with the exception that it is rarely (if ever) seen in the dense 

 forest, although often luxuriating in the shade of the " tea-tree scrub." As 

 might be predicted of a plant having such a wide range of habitats, it is ex- 

 tremely variable. Small specimens are often seen barely two inches in 

 height, with a narrow leaf and single small flower. Every intermediate can 

 be traced between this and the large stout form eighteen inches, or even 

 two feet, high, with a broad leaf, and a spike of from ten to twenty large 

 flowers. The colour of the flowers is iTSually white, but pink and blue 

 flowered varieties are common. 



The perianth differs from that of most Orchids in being composed of six 

 nearly equal leaflets, which spread on all sides when expanded ; so that the 

 flower has little of the irregular and often fantastic appearance of many of 

 its allies, but rather resembles an Ixia or SisyrincJdum. 



The column may be roughly described as hood-shaped, the upper part 

 being produced over and above the anther into a broad three-lobed projec- 

 tion, the middle lobe (which is much the largest) being blunt and smooth, 

 but the lateral ones densely fringed with cilia at their extremities. The 

 anther is placed about half way up the face of the column. It is two-celled, 

 each cell containing two granular plate-like pollen-masses. From each 

 side of the base of the column a low wing-like expansion curves round 

 towards the front of the flower, meeting opposite to the labellum, A small 

 recess is thus enclosed, within which the stigma and rostellum are placed ; 

 both organs being detached from the column proper. The stigma is a 

 broad shield-like body situated in front of and shghtly below the anther. 



