1. A method of automatically harvesting and screening plant embryos in multiple stages, comprising: automatically sorting and singulating plant embryos; automatically classifying the sorted and singulated plant embryos according to their putative germination vigor; and automatically placing those embryos that have been classified as likely to germinate by the classification step onto a receiving surface in a predefined array, wherein the automatic classification is carried out while the embryos are transported on a classification conveyor belt, and the automatic placing of the embryos that have been classified as desirable onto a receiving surface comprises transferring those embryos from the classification conveyor belt to the receiving surface, and wherein the receiving surface comprises a tray mounted on a motorized platform configured to adjust the position of the tray relative to the classification conveyor belt so as to receive the embryos dropping by gravity from the classification conveyor belt into a predefined array.