Notes on the Growing of Seedlings for Physiological Experimentation.

Abstract

For some years past we have carried on rather extensive experimental work 1 with seedlings of the canteloup (Cucumis melo, var.). Much effort has been devoted to the working out of a physically accurate, and at the same time biologically optimal technique. Considerable progress has been made towards the achievement of these desiderata, and it is the purpose of the present paper to report upon the main features of the standard basic technique which we are now using in our seedling work.

Most of our experiments are done under conditions of total darkness, with consequent complete etiolation of the seedlings. In the earlier stages of the work the seeds were germinated in the usual way between layers of moistened filter paper, cotton batting, or cloth, after preliminary soaking in water or some solution. They were then grown in water cultures in accordance with standard plant physiological technique.

All this procedure has now been abandoned in favor of a much better one. The seeds are germinated and grown upon a substratum of agar-agar. The best grade of bacteriological agar is bought at wholesale in bales of 100 or 200 lbs. in order to have a uniform supply over a long period of time. With the bale at present in use in this laboratory a concentration of 1.5 per cent gives the right consistency for the seedling work, niaking a firm, but not too firm jelly. For germination tests with this material, poured in Pyrex glass pie plates to a depth of about one inch, it is only necessary to strew the seeds to be tested on the surface of the agar jelly, and cover the dish with a glass plate to prevent evaporation.