FERTILIZATION 201 



From the cytological as well as the genetical standpoint, it is of 

 considerable interest to know whether the cytoplasm of the male 

 gamete also enters the egg in addition to the nucleus. Finn (1925) 

 considered it probable in Asclepias. Johri (1936a, b) in Sagittaria 

 graminea and Butomopsis lanceolata, and Smith (1942) in Camassia 

 leichtlinii, traced the male gametes as distinct cells up to the time 

 of their discharge into the embryo sac, but were unable to follow 

 the succeeding events in sufficient detail. 



Wylie's (1923, 1941) work on Vallisneria is an important con- 

 tribution to the subject. The male gametes of V. americana main- 

 tain their integrity as cells up to the time they approach the egg 

 (Fig. IIZA-G), and the several cases of physical contact observed 

 between the first male cell and the egg strongly suggest their union 

 as protoplasts rather than naked nuclei (Fig. 113H). Further, the 

 fact that no residue of the first male cell could be seen on the surface 

 of the zygote (as would be expected if only the naked nucleus entered 

 the egg), while the same embryo sac clearly showed the cytoplasmic 

 sheath left behind by the second male gamete, is cited in support of 

 the view that the sperm fusing with the egg functions as a cell and 

 the other as a naked nucleus. 



Some other investigators have, however, denied any participation 

 of the male cytoplasm in fertilization. Considering only the more 

 recent literature, Gurgenova (1928), Gerassimova (1933), and Hoare 

 (1934) mention having observed almost all stages of fertilization in 

 Orobanche ( = Phelipaea) ramosa, Crepis capillaris, and Scilla non- 

 scripta but report only sperm nuclei. Madge (1929) saw male cells 

 in the pollen tubes of Viola odorata but believed that the sheath is 

 lost at the time of syngamy. Breslavetz (1930) studied Melan- 

 drium album, using mitochondrial fixatives, but failed to detect 

 "even the thinnest plasma layer" around the sperm nuclei. In 

 Tulipa (Botschanzeva, 1937) the male nuclei are said to slip out of 

 their sheaths at the time of fertilization; and Trankowsky (1938) 

 and Gershoy (1940) report the gradual disappearance of the male 

 cytoplasm in the pollen tubes of Drosera and Viola. In a recent 

 study of Petunia, Cooper (1946) also implies that the male gametes 

 lose their sheaths at the time of fertilization. 



It seems difficult to set aside all these observations as based on 

 inadequate technique. Nevertheless, Finn and Rudenko (1930), 

 in contradistinction to Gurgenova (1928), were able to see the cyto- 



