There must sometimes be a physical impossibility in the male element reaching the ovule, as would be the case with a plant having a pistil too long for the pollen-tubes to reach the ovarium.
Batzuetan gertatu behar du elementu arrak obulura iristeko ezintasun fisikoa duela, polen-hodiak obulutegira heltzeko pistilo luzeegia lukeen landareari gertatuko litzaiokeen moduan.