FERTILIZATION 211 



X-bodies. In his studies on fertilization Nawaschin observed 

 certain densely staining structures either in the tip of the pollen 

 tube or adjacent to it. Since their exact nature could not be deter- 

 mined, he called them X-bodies. They have been variously inter- 

 preted in different plants and by different authors. In Adoxa 

 they are believed to be the nuclei of the disorganized synergids 

 (Lagerberg, 1909); in Crepis as fragments of the vegetative nucleus 

 (Gerassimova, 1933); in Petunia as the degenerated cytoplasmic 

 sheaths of the male gametes (Cooper, 1946); and in Beta as super- 

 numerary male nuclei in process of disintegration (Artschwager and 

 Starrett, 1933). Some authors have also interpreted them as the 

 nuclei of the adjacent nucellar cells, which become pushed into the 

 embryo sac by the impact of the pollen tube. Tschernojarow 

 (1926) states that in Myosurus they represent the remains of the 

 degenerating megaspores and nucellar cells which lie over the em- 

 bryo sac and are presumably carried into it at the time of entry of 

 the pollen tube. In Datura (Satina and Blakeslee, 1935) there are 

 two X-bodies, one said to be the nucleus of a disorganized synergid 

 and the other the degenerating Vegetative nucleus. 



Wylie (1923) devoted special attention to the nature of the 

 X-bodies in Vallisneria (Fig. 1137). Since the sperms enter the 

 embryo sac as complete cells, he rules out the possibility of the 

 X-bodies being the remains of their cytoplasmic sheaths. The 

 sheaths were also seen intact in the "cystoids" or "tuber-like en- 

 largements" formed by some pollen tubes which terminated in the 

 ovarian chamber without reaching the ovules. The cystoids showed 

 no X-bodies if the vegetative nucleus was still intact, but in those 

 cases in which this was not visible they showed structures which 

 were identical with X-bodies. It is therefore concluded by Wylie 

 that, whatever their origin in other plants, the X-bodies of Vallis- 

 neria are nothing other than the decomposition products of the 

 vegetative nucleus. 



References 



Anderson, E., and Sax, K 1934. A cytological study of self-sterility in Trade- 



scantia. Bot. Gaz. 95: 609-621. 

 Anderson, F. 1922. The development of the flower and embryogeny of Martynia 



louisiana. Bui. Torrey Bot. Club 49: 141-157. 



