In September 1937 I threw some peach kernels (amygdalus) into a box. This box, put away in a corner of the kitchen, drew my attention in June 1938. On June 6th I broke 10 kernels with a hammer, took the flat, dried and hard seeds out and placed them in the hothouse at 20-25 degrees (C) on very wet sphagnum. After two days, on June 8th, the seeds, saturated of moisture, looked like fresh ones. Of 8 seeds I uncovered the germ by operation, removing the membrane that covers them. Two were left undisturbed, as witnesses. After 24 hours I noticed the change in all the individuals that had been operated on; 48 hours later germination was obvious (1). The photo opposite was taken on June 16th. It shows how far germination has progressed with the eight individuals that were operated on, whilst the witnesses did not show any change.
I did not continue the experiment that began to interest me. I felt afraid my passion for botanical research was again getting hold of me.
This experiment gives ground to the opinion I so often expressed: that with many seeds, those of orchids included, the difficulty of germination resides in the weakness of the germ that must pierce the enveloping membrane.
A very ingenious horticulturist, M. Julien Depireux of Gembloux (Belgium), fully trusted my affirmation and proceeded as follows to free the germ of certain seeds that have a difficult germination (I copy his method):
«Immediately after harvesting, steep the seeds during 20 minutes in a bath of sulfuric acid 66°, weakened to one seventh, i.e. one part of sulfuric acid against six parts of water. Take out of the bath, wash several times and sow. The concentration of the bath and the time of immersion must of course vary according to the hardness, the thickness and the chemical composition of the envelopes. For such seeds as are fit for it, one can easily realise the resistance of the envelope by cracking the seed with the teeth. Sometimes several immersions are necessary, followed each time by an examination of the seed, in order to arrive at the total destruction of the envelope, without hurting the germ.»(2)
M. Depireux wrote to me telling of the wonderful results this method gave him... It is a pity that an early death put a stop to the investigations of this very talented breeder.
Freeing the germ helps precipitated germination, i.e. helps greatly to the germination of a seed set free from the ovary at a degree of partial development (vide my essays «Concerning the possibility of provoking etc.» and «Completed working plan»).