Polyspermy and the Endosperm


IN preparing an account of the life-history of Acacia Baileyana, I have found strong evidence of polyspermy in connexion with endosperm formation. The polar nuclei, unfused before fertilisation, have one large nucleolus each. The sperm, which on first contact with the polar nuclei has 13 chromosomes present1 (presumably telophase) (Fig. 1a), proceeds to the resting condition, with a small nucleolus (Fig. 1b). In normal cases this group of two large and one small nucleoli is the most prominent feature of the centre of the sac at this stage. Fusion is first between the sperm and one polar nucleus (Fig. 1c), the product then fusing with the other polar nucleus to form a nucleus with three nucleoli—one small and two large (Fig. 1d). Some instances were found of divergence from the above normal conditions ; for example, there would be in the centre of the sac one nucleus with one large and one small nucleolus, and another nucleus with one large and two small nucleoli (Fig. 2a) ; or there might be altogether four or five small nucleoli (Fig. 2b, c) ; but always at this stage the large nucleoli numbered two. The inference from the above is that sometimes there are more than two sperms to be found in the sac. There was never any indication that more than one sperm became associated with the egg.

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  1. 1

    Newman, I. V., Aust. and N.Z. Assoc. Adv. Sci., 21, 367; 1932.

  2. 2

    Ishikawa M., Ann. Bot., 32, 277; 1918.

  3. 3

    Navashin and Finn, Mem. Acad. Imp. Sd. St. Petersb., 31, 1; 1913.

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