160 



OBSERVATIONS UPON MULING AMONG PLANTS. 



The merely theoretic part of the subject as to the nature of 

 fecundation, whether it be a chemical process or a sort of fer- 

 mentation or engrafting, &c, is but lightly touched ; and we the 

 rather pass it by, as the author's strength seems to lie more in 

 sound judgment and practical observation than in deep thought 

 and minute analysis. As a proof of this, the name of Schleiden, 

 which is of necessity involved in all theories of fructification, 

 whatever may be the views entertained upon the subject, is men- 

 tioned but twice, as far as we have observed, during the course 

 of the volume, and once indeed in reference to the possibility of 

 metamorphosis in cellular plants. 



The next subject which engages the author's attention is the 

 modifications produced by hybrid fecundation. The phaenomena 

 exhibited by artificial impregnation with the proper pollen are 

 precisely the same with those which occur in natural impregna- 

 tion ; but with strange pollen it is not exactly so. The fluid 

 secreted by the stigma is collected in greater abundance on its 

 surface, not as it should seem from increased excitability, but 

 from difficulty of absorption, since in cases where no pollen is 

 applied, or one entirely inoperative, the surface remains for a 

 long time moist ; and in hybrid fecundation, the duration of this 

 condition is in exact proportion to the elective affinity between 

 the mother plant and the particular species whose pollen is 

 applied. 



The process of complete cohesion of the pollen to the stigma 

 takes place somewhat slower than under normal conditions, 

 though its pure colour changes at the same period when im- 

 pregnation is effected. Under the contrary circumstances, the 

 grains may still be seen upon the stigma unaltered after the lapse 

 of some days. A greater quantity of pollen also, applied at 

 different times, is often necessary — a circumstance dependent 

 clearly on the different condition of the stigma. In some rare 

 cases the adventitious pollen produces disorganization of the 

 stigmatic surface, without effecting fecundation, which is usually 

 followed by the speedy disorganization of the stigma, and soon 

 causes the blossom to fall. In general, however, the blossom lasts 

 longer after hybrid fecundation, though sometimes it shrivels 

 early, and contracts upon the stigma without falling off, which it 

 would do in natural fecundation. The degree of sexual attraction 

 between the species under observation is usually the inverse mea- 

 sure of its duration. The success of an experiment may often be 

 anticipated from this law. A large portion of the ovules usually 

 die, which is not surprising, inasmuch as the hybridizing process 

 takes place with difficulty, and probably fewer pollen tubes pene- 

 trate into the cavity of the ovary. The author ascribes this to 

 the impaired vital powers of the organs of the matrix, and a sort 



