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2. 1925b. Heteroploidy and somatic variation in the Dutch flower bulbs. The anat. Rec.31, 348–349.
3. 1926. Heteroploidy and somatic variation in the Dutch flowering bulbs. The Amer. Naturalist60, 334–339.
4. 1928a. Change of the number of chromosomes and its cause. Berichte des zehnten internationalen zoologischen Kongresses, Budapest. 598–602.
5. 1928b. Producing at will of fertile diploid and tetraploid gametes inDuc van Tol, Scarlet (Tulipa suaveolens Roth). Beiblatt Nr. 15 zur Vjschr. naturforsch. Ges. Zürich73, 73–97.