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THE AMERICAN NATURALIST, [Vol. XXXVIII. 



established the fact for certain forms that the first is heterotypic 

 and the second homotypic, exactly as in divisions of the micro- 



FiG. 15. — Embryo sac or megaspore mother-ceil of spermatophytes. a, b^ Galtonia candicans. 

 ai, first mitosis in megaspore mother-cell, az, second mitosis, a^, group of four mega- 

 spores. 61 and i>2, shortly after metaphase of the first mitosis (heterotypic). ^3, meta- 

 phase of the second mitosis (homotypic). c, d, Scilla Sibirica. ci, megaspore moihe^- 

 cell. C2, after the first mitosis, ^3, after the second mitosis, the lower cell of the pair to 

 become the embryo sac. C4, after the second mitosis, the upper cell of the pair to become 

 the embryo sac. di, anaphase of the first mitosis (heterotypic). ^2, anaphase of the sec- 

 ond mitosis (.homotypic). e,Lilium. martagonx portion of embryo sac mother-cell, nucleus 

 surrounded by a felt of fibrill^. _/, Lilinnt candiduvt\ embryo sac mother-cell, nucleus 

 surrounded by radiating fibrillaj. g, h, i, Lilium >nartagon. g, late prophase of first 

 mitosis in embryo sac mother-cell, a multipolar spindle, k, anaphase of first mitosis 

 (lieterotypic). /, anaphase of second mitosis (homotypic). {a, b, c, d, after Schniewind- 

 Thies : 01 ; e,/, g, h, i, Mottier '97.) 



spore or pollen mother-cells. Schniewind-Thies (:oi) figures 

 very completely the mitoses in Galtonia. The first mitosis in 

 the megaspore mother-cell (Fig. 15^:) is heterotypic because the 



