Mr Don ofi the trritabiUty of the Stigma in Pinus iMriac. 43 



diameter as well as tx) the axis of the ball of the eye, is one of the 

 characters by which the fully developed human eye is distinguish- 

 ed, both from the eye of the foetus, and from that of animals. 



On the Irritability of the Stigma, and on the origin and nature 

 of certain parts of the Fructification in Piniis Larix. By 

 Mr David Don, Libr. L. S., Member of the Imperial Aca- 

 demy Naturae Curiosorum, of the Royal Botanical Society of 

 Ratisbon, and of the Wernerian Society of Edinburgh, &c. 

 (Communicated by the Author). 



XT is a well known fact, that certain plants themselves, but 

 more generally particular organs, are endowed with a species of 

 irritability analogous to that observable in the animal kingdom. 

 While engaged in examining the female flowers of the common 

 Larch, during the last spring, in order to satisfy myself respect- 

 ing the real nature of the stigma, I was much surprised by the 

 remarkable degree of irritability observable in that organ, a cir- 

 cumstance which I am not aware had ever been before noticed. 

 That the cucullate processes at the base of the ovaria are the 

 true stigmata, is a point so fully established, as to render im- 

 necessary any additional facts in its support. To regard the 

 ovaria as naked ovula, and that impregnation takes place by the 

 pollen being immediately shed on their surface, instead of being 

 conveyed by means of an organ analogous to the stigma of other 

 plants, are opinions by far too paradoxical to admit of belief. 

 These cftcullatc processes, when fully mature for the reception 

 of the pollen, expand, and their inner^surface is then clothed with 

 innumerable minute papillae. I took a branch bearing unimpreg- 

 nated female flowers, and having dusted them with the pollen 

 from the ripe male catkins of another branch, I found on exa- 

 mination the cucullate stigmata completely filled with the pol- 

 len, and I could readily perceive the sides of the female organ 

 contract gradually, until they finally became completely collapsed. 

 The pollen in Coniferat being composed of minute vesicles filled 

 with a prolific fluid, the collapsing of the sides of the stigmata 

 is evidently for the purpose of pressing out the contents of these 

 vesicles, and forcing the fluid through the narrow duct on to the 



