84 



GENERAL REVIEW OP THE ORCHIDEiE. 



...N 



( if the flower. From the apex or top of the anther a to the base 

 of the ovary it is nearly three inches long, although shown 

 upright in the figure it slightly arches forward from below the 

 stigma s to the apex; the part so bent is thence parallel with 

 the labellum, which is in fact appressed to it and enfolds it 

 with its side lobes, a circumstance that immensely facilitates 

 the pollination of the stigma by insect agency. The stigraatic 

 cavity is separated from the anther by a tongue-shaped rostellum 

 R ; the stigmatic surface is coated with a thick layer of 

 transparent viscid matter which holds the pollinia when applied 

 to it with extraordinary tenacity. The pollinia are four in 

 number ; each pollinia or i)ollen-niass is a waxy flattened disk 

 nearly the shape of an artist's pallet ; the pollinia are attached 

 to semi-transparent ribbon-like appendiculse, which are also 

 covered with pollen grains. The ovary is cylindric and is 

 traversed longitudinally by three equidistant sunk lines. Figure 2 

 represents a longitudinal section of the column and ovary, 

 twice natural size, in which the position of the pollinia, 

 rostellum and stigma are sliown by the letters p, a and s 

 respectively ; D is the duct or canal leading from the 

 stigma to the ovary and down which the pollen tubes 

 pass ; this canal in transverse section has the form of 

 a W-shaped curve extending through the central part of 

 the column where it is thickest ; it is filled throughout 

 with conducting tissue of very loose consistency, and 

 formed of greatly elongated cells overlapping at their 

 ends. The narrow slit at N is the nectary that penetrates 

 into the ovary and in which honey is freely secreted ; 

 ()V is the immature ovary ; the parts of the ovary arc 

 shown more distinctly in fig. 3 of a transverse section 

 twelve times enlarged. Each placenta at this early stage 

 consists of two thickened plates; the papillae that ultimately 

 develop into ovules are placed along the projecting 

 angles of these plates. The "W-shaped duct along which 

 the pollen tubes pass in their passage from the stigma to 

 the ovary is shown in fig. 4, a section of the column made 

 just below the stigma, and like the preceding figure twelve 

 times enlarged. 



On the 1st of June, 1885, forty-five flowers of Catthija 

 Mossue were selected for pollination ; these flowers were 

 divided into three sets of fifteen each, of which one set 

 was fertilised with their own pollen, a second set with 

 })ollen of different flowers l)ut of the same variety, the 

 third set with the pollen of flowers of a different species, 

 Lcelia purpurata^ the whole of the pollinia being applied 



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