In one aspect, the present invention provides methods of producing conifer cotyledonary somatic embryos from pre-cotyledonary embryos. The methods of this aspect of the invention include the step of (a) dispensing a plurality of pre-cotyledonary embryos onto a porous material horizontally disposed over a non-porous surface in a volume of sterile dilution medium sufficient to submerge at least the surface of the porous material, thereby uniformly dispersing the pre-cotyledonary embryos； (b) removing the sterile dilution medium from the non-absorbent porous material, thereby trapping the uniformly dispersed pre-cotyledonary embryos on the porous material； and (c) contacting the pre-cotyledonary embryos trapped on the porous material with development medium for a period of time sufficient to produce conifer cotyledonary somatic embryos.
