368 Mr Brown an the Existence of Active Molecules 



nor in any other tribe examined, have I ever been able to find 

 them in any part of the female organ, except the stigma. Evert 

 in those families in which I have supposed the ovulum to be 

 naked, namely, Cycadeae and Coniferae, I am inclined to think 

 that the direct action of these particles, or of the pollen contain- 

 ing them, is exerted rather on the orifice of the proper mem- 

 brane than on the apex of the included nucleus ; an opinion 

 which is in part founded on the partial withering confined to one 

 side of the orifice of that membrane in the larch, — an appearance 

 which I have remarked for several years. 



To observers not aware of the existence of the elementary 

 active molecules, so easily separated by pressure from all vege- 

 table tissues, and which are disengaged and become more or less 

 manifest in the incipient decay of semitransparent parts, it would 

 not be difficult to trace granules through the whole length of the 

 style : and as these granules are not always visible in the early 

 and entire state of the organ, they would naturally be supposed 

 to be derived from the pollen, in those cases at least in which 

 its contained particles are not remarkably different in size and 

 form from the molecule. 



It is necessary also to observe, that in many, perhaps I might 

 say in most plants, in addition to the molecules separable from 

 the stigma and style before the application of the pollen, other 

 granules of greater size are obtained by pressure, which in some 

 cases closely resemble the particles of the pollen in the same 

 plants, and in a few cases even exceed them in size : these par- 

 ticles may be considered as primary combinations of the mole- 

 cules, analogous to those already noticed in mineral bodies and 

 in various organic tissues. 



From the account formerly given of Asclepiadeae, Periploceae, 

 and Orchideae, and particularly from what was observed of As- 

 clepiadeae, it is difficult to imagine, in this family at least, that 

 there can be an actual transmission of particles from the mass of 

 pollen, which does not burst, through the process of the stigma ; 

 and even in these processes I have never been able to observe 

 them, though they are in general sufficiently transparent to show 

 the particles, were they present. But if this be a correct state- 

 ment of the structure of the sexual organs in Asclepiadeae, the 

 'question respecting this family would no longer be, whether the 

 particles in the pollen were transmitted through the stigma and 



