Because the gene conditioning fasciation exhibits incomplete penetrance, the character may assume any of many degrees of expression. Pressure Underground shoots that pierce the ground, such as asparagus, tend to become fasciated. Seasonal Influences Time of sowing may influence the degree of fasciation, with earlier sowing appearing to produce larger numbers of fasciated plants. Crowding has often been reported to produce a decrease in the percentage of fasciated plants. Temperature Low temperature followed by high temperature causes fasciation in Hyacinthus and may be a cause of fasciation in other plants.
Defoliation produces a similar reaction.
Wounding of the Growing Point Wounding causes fasciation as well as all kinds of abnormalities. Conclusions Fasciation can be caused by a variety of natural and artificial agents. From the literature, it appears that few cases of fasciation have been shown to be caused by insects, although most reports of fasciated plants contain no information as to what may have induced the fasciation. Information is clearly needed in order to find out the relative importance of the above-listed agents. Acknowledgement Brain S. Rushton's comments and corrections are much appreciated.