Read the following passage carefully:
In July 1894, botanist Dr. Samuel Oakes published his seminal research paper on subterranean fern germination. Although the publication marked the formal conclusion of his project, the pivotal breakthrough had occurred four years prior, in 1890, when he discovered a blooming *Cryptocoryne* specimen inside a humid Yorkshire cave. Before leaving the cave to return to his laboratory, Dr. Oakes preserved several root specimens in alcohol. Two years after collecting these initial samples, in the autumn of 1892, he successfully synthesized an artificial growth medium that replicated the cave's mineral composition. Having established this medium, Dr. Oakes spent the following winter of 1893 conducting controlled temperature trials in a greenhouse, which yielded the empirical data compiled for his eventual publication.
Based on the passage, arrange the following events in the correct chronological order from earliest to latest.
- 1Dr. Oakes preserved root specimens in alcohol at the cave site.
- 2Dr. Oakes synthesized an artificial growth medium replicating the cave's mineral conditions.
- 3Dr. Oakes conducted controlled temperature trials in a greenhouse.
- 4Dr. Oakes published his seminal research paper on fern germination.