106 Mr. Brown on the Organs and Mode of 
power of 150. With a power of 300 or 400 indeed, extremely 
minute and very transparent granular matter may be detected ; 
but such granules are very different from those which have been 
supposed to belong to the grains of pollen. 
As an entire pollen mass is usually applied to the surface of 
the stigma, and as a great proportion of the mass so applied is 
acted upon by the fluid in which it is immersed, the tubes pro- 
duced are generally very numerous, and together form a cord 
which passes through the channel of the stigma or style. 
On reaching the cavity of the ovarium this cord regularly 
divides into three parts, the divisions being closely applied to 
those short upper portions of the axes of the valves which are 
not placentiferous ; and at the point where the placenta com- 
mences each cord again divides into two branches. ‘These six 
cords descend along the conducting surfaces already described 
when speaking of the unimpregnated ovarium, and generally 
extend as far as the placentz themselves, with which they are 
thus placed nearly but perhaps not absolutely in contact. 
The cords now described, both general and partial, seem to 
me to be entirely composed of pollen tubes, certainly without 
any mixture of the utriculi of the stigma, or, as far as I can © 
ascertain, of the tissue of the conducting surfaces. 
In two cases, namely Ophrys apifera and Cypripedium spec- 
tabile, I at one time believed I had seen tubes going off laterally 
from the partial cords towards the placente and mixing with 
the ovula; but I am not at present entirely satisfied with the 
exactness of these observations, and I have never been able to 
detect similar ramifications in any other case *. 
'That the existence of these tubes in the cavity of the ovarium is 
essential to fecundation in Orchidez, can hardly be questioned. 
But the manner in which they operate on, or whether they come 
* See Additional Observations. 
actually 
