164 MR. J. SCOTT ON THE STERILITY AND CROSS-IMPREGNATION 
the pollinia of O. divaricatum eupreum,1 fertilized upwards of 200 
flowers with own pollinia, yet every capsule proved abortive. That 
this inveterate abortion of the capsules was neither due to the non- 
emission nor to the non-penetration of the pollen-tubes, I satisfied 
myself by the dissection and examination of the columns of many 
of these flowers as they dropped off, and in all I invariably found 
an abundance of pollen-tubes. 
Such then is a brief abstract of the experiments illustrative of 
the peculiarities in the reproductive economy of certain species of 
Oncidium, as communicated to the Botanic Society of Edinburgh, 
and I will now proceed to give in fuller detail a series of experiments 
which I have lately made on the above and other species of Onei- 
dium in the Royal Botanic Gardens of Edinburgh, as further illus- 
trating the capriciousness of their relations in respect to fertility. 
Those which I have now to record were performed upon two 
perfectly self-sterile plants of O. microchilum—respectively given 
in the sequel as Nos. 1 and 2—and plants of the O. ornithorhynchum 
and O. divaricatum cupreum ; they are as follows :— 
First, I inserted pollinia of O. microchilum (No. 2) into the 
stigmatic chamber of eight flowers of the O. ornithorhynchum ; of 
these, three produced capsules containing about 21 per cent. of 
good seed. I also tried the converse experiment, and applied 
pollinia from the O. ornithorhynchum to the stigmatic chambers of 
twelve flowers of the O. microchilum (No. 2), but in this case I 
failed in causing a single capsule to swell. To satisfy myself that 
this abortion of the capsules was not simply due to the non- 
development of the pollen-tubes, I dissected the columns of many 
of the flowers, and found in each an abundance of pollen-tubes. 
Secondly, I inserted pollinia from the O. mierochilum (No.1) into 
the stigmatie chambers of eight flowers of the O. ornithorhynchum, 
and obtained five capsules. Of these one was perfectly developed, 
but yielded no good seed ; the others, however, were well developed, 
and yielded about 16 per cent. of good seed. Itried the converse 
experiment likewise, and applied pollinia from the O. ornitho- 
rhynchum io the stigmatie chambers of twelve flowers of the 
O. microchilum (No. 1), yet I failed to obtain a single good 
capsule, though I had hopes, from the early development of two 
of them, that the results would have been otherwise; both dropped 
prematurely, although on dissection of the columns of several 
of the flowers I found an abundance of pollen-tubes. As shown, 
however, the pollinia of the O. ornithorhynchum in the present as 
in the above case, though thus absolutely ineffective in the 
fertilization of O. microchilum (No. 1), are nevertheless good, 
