THE MALE GAMETOPHYTE 



137 



cells and nuclei have been described, but it is evident that the 

 form as well as the size may change decidedly in the course of 

 its history. For example, SchafTner 31 notes that the male nuclei 

 in Sagittaria are at first spherical, but after pollination become 

 bean-shape or spindle-shape. In Silphium Merrell 48 observed 

 the originally spherical male nuclei become much elongated, more 

 or less curved, and even spirally twisted while still within the 

 pollen-grain (Fig. 64) ; and in Triticum and other grasses Go- 

 linski 21 implies the same changes in 

 form in describing the occurrence of 

 male nuclei within the pollen-grain 

 as " not unlike the antherozoids of a 

 fern or of Cham." It has been re- 

 peatedly observed that the spherical 

 nuclei of the oblong or lenticular 

 male cells of Lilium increase in size 

 and become vermiform and variously 

 curved and coiled after discharge 

 from the pollen-tube, and the same 

 phenomenon was observed by Miss 

 Thomas 53 in Caltha. 



It seems to be generally true that 

 the male cells when formed free in 

 the body of the grain are at first 

 spherical, but soon become oblong or 

 lenticular. In a forthcoming paper 

 by Koernieke it will be shown that in 

 Lilium only male nuclei are found in 

 the pollen-tube; at least there are no 

 male cells as ordinarily figured. This 

 claim is of special interest, since in 

 Lilium male cells are clearly organized in the pollen-grain. 

 The increase in size and change of form so often described as 

 taking place in the tube or sac are probably phenomena of the 

 male nucleus rather than of the male cell. There are well- 

 known cases, however, in which the spherical or oblong form 

 persists throughout the history of the nucleus. For example, in 

 Peperomia (Johnson 49 ) the male nucleus is spherical even in 

 contact with the egg, and the same is true of several other forms 

 recently investigated in connection with double fertilization. 



Fig. 64. — A, microspore of SilpM- 

 um integrifolium, showing tube- 

 nucleus and two male nuclei. 

 B, later stage in S. terebinthina- 

 ceum, showing the two male 

 cells. C, single male cell of S. 

 integrifolium, showing spiral 

 form. — After Merkell. 48 



