58 Fertilization of Plants. [Ji^ilyj 



produced grains, but they were very small, yet perfect. They 

 germinated and produced the characteristic flowers of the species, 

 from which the pollen was derived, which was different from the 

 species to which it was applied. 



It would seem that a portion of the pollen was expended in 

 some other way than in the direct act of fertilization. Perhaps 

 the singular phenomenon of the elevation of temperature during 

 impregnation, may be in some manner dependent on the action of 

 the pollen. Although this phenomenon is not proved in all cases, 

 and in fact in comparatively very few, yet it would seem to be 

 probable that the imperfection of the instruments might be the 

 cause. The thermo-electric needles of M. Bicefuerel have ope- 

 rated very satisfactorily in the hands of Schultz, Broghniart, and 

 Dutrochet; and we may hope that by some such means this ele- 

 vation of temperature during fertilization may be proved to be a 

 universal fact. 



Experiments on the subject are very liable to be vitiated by 

 the unnatural circumstances under which the subject for experi- 

 ment is placed. In experimenting on the tomato in relation to 

 its fecundation, during the winter and early spring, the plants 

 were of course grown within doors. They grew vigorously and 

 bloomed abundantly, but fertilization did not take place at all. 

 The pollen was abundant on the stigma, but no pollen tubes were 

 emitted, and of course the flowers decayed, turned yellow, and 

 fell off. We suspected the cause of failure, and after allowing 

 the plants to bloom and cast their fleece till they could be re- 

 moved into the open air, they were put out, and every flower that 

 opened after such exposure on examination was found to contain 

 pollen that emitted tubes, and then undisturbed produced fruit and 

 seeds. In this case the atmosphere in which they grew was too 

 dry, and the stigma did not yield moisture enough to burst the 

 pollen grains, as they would burst readily-on a wet surface, under 

 the microscope. Similar causes of failure may be frequent, and 

 we may be assured that unless the natural conditions of the plant 

 are supplied, it is in vain to expect perfection in vegetation. 



3. The effect of the action of the pollen on the embryo is im- 



