Pollen tube through wind, water or pollinators. The last step before fertilization is the growth of the pollen tube to transfer non-motile sperm to the protected egg. Pollen tubes are unique to plants and their structure had evolved over plant history. The pollen tube formation is complex and the mechanism is not fully understood, but is of great interest to scientists. Pollen is produced by the stamen, the male reproductive organ of the flower. Each pollen grain contains a vegetative cell, and a generative cell that divides to form two sperm cells. The pollen is delivered by the opening of anthers for
Shroud of Turin in Edessa, Turkey. Mark Antonacci argues that the pollen evidence and flower images are inherently interwoven and strengthen each other. However it was subsequently determined that Baruch's work was "scientifically unsafe", and Danin thereafter disowned the publication of this work. Danin stated in 2011, that: "In 2001 we brought most of the slides to Prof. Dr. Thomas Litt who is an expert palynologist and has very sophisticated microscopic equipment. Prof. Litt concluded that none of the pollen grains he saw could be named at a species level. Hence, all the conclusions drawn from previous palynological investigations of Dr. Frei's material