OF CERTAIN SPECIES OF ONCIDIUM. 165 
as I have proved by their applieation to their own stigmas 
as well as to those of O. pumile, fertile unions having in several 
instances been thus effected. 
Thirdly, I inserted pollinia of O. microchilum (No. 2) into the 
stigmatic chambers of six flowers of the O. divaricatum cupreum, 
and obtained three capsules, which yielded about 36 per cent. of 
good seed. I likewise tried the converse experiment, and applied 
pollinia of the O. divaricatum cupreum to the stigmas of six 
flowers of the O. microchilum (No. 2), yet though two of these 
produced capsules, I could not, after a most careful examination 
of their contents, detect an embryonated seed. I repeated this 
experiment on twelve other flowers with even less success than 
before, as every capsule aborted. 
Fourthly, I inserted pollinia of O. microchilum (No. 1) into the 
stigmatic chambers of six flowers of O. divaricatum cupreum, and 
obtained four capsules, which contained about 34 per cent. of good 
seed. By the converse experiment I had, from six flowers of the 
O. microchilum (No. 1), impregnated by pollinia of O. divaricatum 
cupreum, two capsules, which yielded 42 per cent. of good seed. 
Fifthly, I inserted pollinia of O. microchilum (No. 2) into the 
stigmatie chambers of six flowers of the O. microchilum (No. 1), 
and obtained five capsules, of which four were good, yielding about 
75 per cent. of embryonated seeds. T also tried the converse 
experiment, and applied pollinia (known to be good from their 
action on other species) of O. microchilum (No. 1) to the stigmas 
of six flowers of O. microchilum (No. 2), but in this case every 
capsule aborted. Struck with the great difference in the results 
of these reciprocal crosses, I repeated the last experiment, and 
impregnated in the same manner twelve other flowers of the O. 
mierochilum (No. 1), but the result was similar, all the flowers 
proving abortive. 
Sixthly, I impregnated twelve flowers of O. microchilum (No. 1) 
by its own pollen, yet not one produced a capsule. I repeated 
this experiment on twelve other flowers with the same result. 
The insusceptibility of this plant to fertilization by its own pollen 
interested me, so that I again and again repeated the experiment, 
but the foregoing results were repeated, not one capsule ever 
having set. I may state that on dissection of the columns of a 
number of these flowers, I invariably found them abundantly 
permeated by the pollen-tubes. 
Seventhly, I impregnated twelve flowers of O. microchilum 
(No. 2) by its own pollen; nevertheless, though in this instance 
again pollen-tubes were freely developed, they failed in effecting 
