40 PLANT HYBRIDIZATION BEFORE MENDEL 



parts, are described at some length, and the pollination discov- 

 ered to be by means of humble-bees. 



From his experiments with the Iridaceae and Malvaceae, Kol- 

 reuter concludes : 



"l have instituted very many and various experiments and observa- 

 tions, w^hich have completely convinced me that the pollination of the 

 stigmas (in the two groups mentioned) is not to be ascribed either to 

 the location which the parts of the flower have to one another, nor to 

 the wind, but simply to the insects alone." (p. 25.) 



Kolreuter also comments on the fact that: 



"if one takes away at the same time from a certain number of flowers 

 their still closed anthers, yet their stigmas will always be covered over 

 with a sufficient quantity of pollen, which the insects carry thither from 

 other flowers standing in the neighborhood." (p. 27.) 



Thus concludes the general botanical discussion in Kolreuter's 

 first Nachricht, which occupies a space in the Oswald edition of 

 28 pages, and which has been discussed at length because it is 

 seldom commented upon, and because it shows the preliminary 

 preparation for his hybridization experiments which Kolreuter 

 obtained through natural history investigations at first hand. 



The development of the pollen tube was not known in Kolreu- 

 ter's time, having been first observed by Amici in Portulaca in 

 1823; the penetration of each pollen tube into the ovary and to 

 the micropyle of the ovule, by the same investigator in 1830; 

 and the development of the embryo from an egg cell already 

 present in the embryo-sac before the arrival of the pollen-tube, 

 which stimulates it to further development, also by Amici in 

 1846. (Sachs, "Hist, of Bot.," 432.) The number of 50-60 

 pollen grains, found by Kolreuter by experiment to be the mini- 

 mum number requisite for the fertilization of the 30 or so seeds 

 in a capsule, represented to Kolreuter's mind in a manner the 

 mass amount of the "exudate" required. This latter was sup- 

 posed, as stated, to be excreted by compression from the matur- 

 ing pollen grain upon the stigma, there absorbed, and drawn 

 through special conduction or secretion canals into the interior of 

 the ovary. 



One can, Kolreuter continues (p. 21), by exposing the female 

 flowers to the wind, while excluding the approach of insects, con- 

 vince himself, through the immediately succeeding death of the 

 ovary, that pollination in such plants could not occur by means 



