508 ON THE ORGANS AND :\I01)E OP FECUNDATION 



of tlie stigma, and as a great proportion of the mass so 

 applied is acted upon by the fluid in which it is immersed, 

 the tubes produced are generally very numerous, and to- 

 gether form a cord which passes through the channel of the 

 stigma or style. 



On reaching the cavity of the ovarium this cord regu- 

 larly 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 commences each cord again divides into two 

 branches. These six cords descend along the conducting 

 surfaces already described when speaking of the unim- 

 pregnated ovarium, and generally extend as far as the 

 placentae themselves, with which tliey are thus placed 

 nearly but perhaps not absolutely in contact. 



The cords now described, both general and partial, seem 

 to me to 1)0 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 sur- 

 faces. 



In two cases, namely Ophrys ajnfera and Cypri2')edium, 

 spectabile, I at one time believed I had seen tubes going off 

 laterally from the partial cords towards the placentae 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 Orchideae, can hardly 

 be questioned. But the manner in which they operate on, 

 707] or whether they come actually in contact with, the ovula, 

 are points which still remain undetermined. 



I am aware that Professor Amici/ who discovered in 

 several plants the remarkable fact of the penetration of the 

 pollen tubes into the cavity of the ovarium, and Avho re- 

 gards this economy as being very general, likewise believes 

 that in all cases a pollen tube comes in contact Avith an 



^ See Additional Observations. 

 = Atnial. des Sc. Nat. xxi, p. 329. 



