UNCTION.] OVULE TUBES AND POLLEN TUBES. 285 



or universal existence of pollen tubes.* Such processes, 

 observes M. Decaisne, exist, indeed, " in some plants ; but in 

 others, where papillae are situated upon the ovule, as in Arads, 

 they have never been observed, and the papillae seem to be 

 substituted for them; in other plants again, little bands 

 descend from the base of the style, and are deposited in the 

 seed near the micropyle ; for instance, in Composites and 

 some others." 



Dr. Dickie, of Aberdeen, has carried this remark further, 

 and has shown, that in many plants the tubes found, at the 

 time of impregnation, in the foramen of the ovule, really 

 originated there, and were not derived from the pollen. His 

 very curious observations will be found at length in the 17th 

 vol. of the Annals of Natural History, to which the reader is 

 referred. He has ascertained their existence in plants 

 belonging to Cucurbits, Chenopods, Buckwheats, and Sandal- 

 worts; to which may be added Rushes, several Figworts, 

 (Scrophulariaceae) Parnassia, and probably Orchids. 



By some it has been thought that the molecular motile 

 matter found in the interior of pollen grains represented the 

 germs of future embryos, and that the introduction of one 

 such molecule into an ovule was necessary in order to insure 

 the production of an embryo. But it has been shown that 

 the molecules are starch : upon this matter Schleiden has the 

 following remarks : 



" It appears to me, that the very minute chemical and 

 microscopical researches of Fritsche on the pollen (Peters- 

 burg, 1837) have made an end of the so called pollen ani- 

 malcules; for it would be contrary to the laws of animal 

 nature, that the lively motions of these apparent infusoria 

 should continue undisturbed after the addition of alcoholic 

 solution of iodine (a poison that immediately kills all infu- 

 soria and animal spermatozoa), as Fritsche states to be the 

 case, and which in many instances I have observed. 



" In the (Enotherse, however, to which Meyen has par- 

 ticularly referred, I have not been able to see anything of 



* Gasparrini asserts that the pollen of the Orange tree has no power of 

 omitting pollen tubes. 



