BIBLIOGRAPHY 103 
. The experiments of Miyoshi (8) by which he showed that 
pollen tubes will penetrate the cut end of a style and travel toward 
the stigma, and that when a lateral cut is made into the conduc- 
tive tissue the pollen tubes will grow out in various directions, we 
maintain not only do not support his view that the pollen tubes are 
guided in a purely mechanical way, but also that they do not 
contradict the suggestion of such a differential distribution of an 
appropriate stimulant, inasmuch as a cut in the conductive tissue 
would in all probability set up disturbances by which the ordinary 
distribution of the stimulant might be reversed. 
It may, of course, be that Miyoshi's contention is true for the 
style, although I believe that the case is not proven ; but that the 
pollen tube is guided in one way in one region of the conductive 
tissue, and in another way in another, seems quite improbable. 
3. The suggestion is submitted that the synergidae are the 
source of the stimulant, and constitufe the center of distribution 
of the stimulant. To this idea I am led by the cytological char- 
acter of those cells, and by their position as the only effective 
center, exclusive of the egg itself. We do not forget the experi- 
ment of Strasburger (21) on Torenia, the results of which were, 
however, negative. Searching experimentation is still needed to 
throw light on the perplexing problem which we have attempted 
somewhat further to elucidate. 
A A List OF LITERATURE PERTAINING TO THE POLLEN TUBE. 
1. Benson, M. Contributions to the Embryology of the Amentiferae, 
Part I. Trans. Linn. Soc. Bot. 3: 409. 1894. 
Capus, G. Anatomie du tissu conducteur. Ann. des sci. nat. Bot. 
VI. 7: 209-291. 1878. 
Dalmer, M. Ueber die Leitung der Pollenschlauche bei den Angio- 
spermen. Jen. Zeitschr. 14: 1-39. 
. Koernicke, M. Studien an Embyrosack-Mutterzéllen. Sitzungsber. 
d. Niederrhein. Gesellsch. Natur. und Heilkunde zu Bonn. 4 
Mar. 1901. 
Lang, F. X. Untersuchungen iiber Morphologie, Anatomie und 
Samenentwickelung von Polypompholyx und Byblis gigantea. . Flora, 
88: 149-206. 1901. 
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