Holger Jørgensen: The Germination of the Pollen-mass etc. 19 



liquid, long pollen-tubes in a very dense liquid. This then agrees 

 well with what has been said above of the reason of the growth of 

 the pollen-tubes. In the style the pollen-tubes do not twine. 



4. The twinings of the pollen-tubes in culture may be explained 

 by the assumed chemotropy, there being in culture a great chance 

 of unilateral influence upon the pollen-tubes. 



5. In Campanula rotundifolia and in Linaria vulgaris it has 

 also been shown to be probable that the pollen-tubes in order to 

 grow require a gradual rising of the concentration of the nutrient 

 solution. 



Literature. 



1. Ehrenberg: Ueber das Pollen der Asclepiadeen. Berlin 1831. 



2. Rob. Brown: On the organs and mode of fecundation in Orchideæ 

 and Asclepiadeæ. Trans. Linn. Soc. XVI, 1833. 



3. Corry: On the structure and development of the Gynostegium etc.,. 

 Trans. Linn. Soc. 2. ser. vol. 2. 1881—87 Bot. 



4. Molisch: Zur Physiologie des Pollens etc. — Sitzungsber. d. k. Akd. d. 

 Wiss. in Wien, mat. nat. Kl. Bd. CII Abt. I, 1893. 



5. Gager: The development of the pollinium etc. — Annals of botany 



XVI, 1902. 



6. Hal s ted: The germination of pollen. — Bull of the Torrey Bot. Club. 

 Vol. 16, 1889. - 



7. Elfving: Studien über die Pollenkörner der Angiospermen. — Jenaische 

 Zeitschr. f. Med. u. Naturw. 1879. 



8. Strasburger: Ueber fremdartige Bestäubung. — Pringsh. Jahrb. Bd. 



XVII, 1886. 



9. Lidforss: Zur Biologie des Pollens. - Pringsh. Jahrb. 29, 1896. • 



