Reproductive Organs of the Misseltoe. 187 



numerous scattered granules, from the external envelope, 

 which is bristled over with minute asperities. When the 

 grain is completely matured, a similar pressure causes the 

 protrusion, from the same envelope, of a vesicle, which, on 

 being itself burst, emits a multitude of granules ; but there is 

 no appearance of a nucleus. 



On reviewing the above series of changes, we perceive that 

 the formation seems generally to proceed from the exterior 

 towards the interior, seeing that the vesicles are organized 

 and filled with granules, in the midst of which are observed 

 many centres [moules), which, to the number of four, associate 

 or absorb the rest of the granules ; that these vesicles become 

 thickened by the formation of successive layers more and 

 more internal, and are divided by their interposition between 

 the granular centres ; that these centres are invested with a 

 primary envelope, which is finally lined on the inside by a 

 final membrane, which immediately encloses the granules. 

 These different parts are not co-existent, the older ones dis- 

 appearing first, and probably furnishing the materials for the 

 more recent, of which, in other respects, they do not consti- 

 tute a part. 



These observations accord both with those which are con- 

 sidered the most complete and certain on the formation of 

 tissues, as well as with those which relate more particularly 

 to the formation of pollen. To this latter phaenomenon they 

 contribute many new facts: such as the presence of these 

 nuclei, the primary germs of the pollinic grains ; the deposi- 

 tion of many successive layers on the walls of the mother 

 utricule, and the instantaneous formation of divisions to 

 which they themselves conduce ; the origin of the proper 

 envelope of the pollen. 



In most other plants, when pollen arrives at maturity, 

 some peculiar change takes place in the cellules constituting 

 the internal walls of the cell, whose zones become thickened, 

 and are finally divided into elastic filaments, whose play de- 

 termines the dehiscence of the anther. Nothing similar to 

 this takes place in the Misseltoe, whose anther can be scarcely 

 said to be dehiscent, inasmuch as its cells are externally open. 

 Moreover, the cellules composing its wall continue in the 

 state above described, their component membrane being per- 

 sistent, and of uniform thickness. 



Nearly at the same time when the pollen has attained per- 

 fect maturity, the female flower is expanded, and the pollinic 

 action is then for the first time able to take effect upon the 

 newly-disclosed stigma. Nevertheless, the most delicate ob- 

 servation has failed to detect the ovulum either at this period 



