170 Mi*. R. Brown on the Existence of active Molecules 



follow them to the nucleus of the ovulum itself. My en- 

 deavours, however, to trace them through the tissue of the 

 style, in plants well suited for this investigation, both from the 

 size and form of the particles, and the development of the fe- 

 male parts, particularly Onagrarite, was not attended with 

 success ; and neither in this nor in any other tribe examined, 

 have I ever been able to find them in any part of the female 

 organ, except the stigma. Even in those families in which 

 I have supposed the ovulum to be naked, namely, Cycadece 

 and Coniferce, I am inclined to think that the direct action of 

 these particles, or of the pollen containing them, is exerted 

 rather on the orifice of the proper membrane 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 re- 

 marked for several years. , 



To observers not aware of the existence of the elementary 

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

 getable 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 vi- 

 sible 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 remark- 

 ably 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 particles may be considered as primary combinations of 

 the molecules, analogous to those already noticed in mineral 

 bodies and in various organic tissues. 



From the account formerly given of Asclepiadece, Peri- 

 plocece, and Orckidete, and particularly from what was ob- 

 served of Asclepiadea?, 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 

 processes 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 pre- 

 sent. But if this be a correct statement of the structure of 

 the sexual organs in Asclepiadetz, the question respecting this 

 family would no longer be, whether the particles in the pollen 



were 



