where, without doubt, fooil materials occur in f^reatcr abundance, 

 however Httlc their actual amount, than in the ovarian cavity. 

 We must therefore conclude, in the absence of further evidence 

 that this behavior may not wholly be determined in the manner 

 asserted by Longo. 



In discussing the facts above outlined, Longo draws the follow- 

 ing conclusions : 



1. The behavior of the pollen tube in following an intercellular 

 path is not connected with its inability to grow freely in an open 

 space. This is to be inferred from the fact that in closely related 

 species the behavior in this respect is different according to the 

 continuity of the conductive tissues. Longo has completely 

 demonstrated the truth of his contention, by showing that the 

 pollen of Huniulus Lupiilns L., and of Cannabis sativa L., * in all 

 of which the pollen tube has an endotropic course, germinates in 

 humid air, and pollen tubes are produced. Experimental evi- 

 dence was obtained in the case of the pollen of certain gymno- 

 sperms [Picca cxccisa, three spp. of Finns) which also germinated 

 and produced tubes in moist air, from which he correctly inferred 

 that the endotropic behavior in angiosperms cannot be due to an 

 inheritance of this trait in the gymnosperms, as was pointed out 

 by INIurbeck.f Clearly, we must, as Longo maintains, abandon 

 the position that the phenomena of ectotropism and endotropism 

 are quite distinct from each other. 



2. Chalazogamy is not primitive in the angiosperms, and this, 

 or in general, the intercellular behavior, is a later phenomenon, 

 and in this, Longo differs from Treub and Nawaschin, but agrees 

 with IMurbeck, who regards such beha\'ior as a physiological 

 peculiarity, and of no meaning from a ph)'logenetic point of view.^ 



3. In plants in which the pollen tube is endotropic, the direc- 

 tion of its growth is determined b}' the presence of a special sub- 

 stance to which it responds chemotactically. This, Longo adds, 

 is developed within the tissues when the course is endotropic 



* Longo, R. 0/>. ci/., p. 21. 



t Murbeck, Sv. Ueber das Verhalteii des Pollenschlauche? bei Alchemilla ar- 

 vensis. Lands. Univ. Arsskrift, 36: 9. 1901. 

 t Murbeck, Sv. Of. at. 



