364 BOTANICAL GAZETTE [jttne 



mcgaspores 



J 



has expressed the opinion privately that these four nuclei are those of 



megaspores 



Panda 



A rtocarp 



At the four-nucleate stage there is the usual arrangement of two 

 micropylar and two antipodal nuclei; but the former do not divide, 

 and the latter give rise to twelve nuclei. If this record is confirmed 

 by tracing the history of the nuclei, there is introduced in this case 

 an irregularity in the succession of divisions. It may be assumed, 

 subject to subsequent observation, that four megaspore nuclei are 

 involved in the formation of these fourteen nuclei ; and the irregularity 

 would consist in the fact that two of them do not divide; that one of 

 the others added two successive divisions (the ehmination of one 

 division) ; and that the remaining one added three successive divisions 

 (the usual number). There is thus no greater number of divisions 

 than usual, and even a certain amount of elimination. It is interest- 

 ing to note that if the two micropylar nuclei do not divide and are 

 really megaspore nuclei, the egg is removed from the mother cell by 

 only two divisions, which is the condition of the animal egg. A 

 careful cytological investigation of these divisions would seem to be 

 most desirable. 



The introduction of a certain amount of irregularity in the succes- 

 sion of divisions is suggested by the records of several species. For 

 example, in Gunnera,^ while eight nuclei are common, any number up 

 to sixteen may be found; and in Trillium grandifioruni^ ten sometimes 

 occur. In neither of these species, however, do we have any informa- 

 tion as to the behavior of the mother cell in forming megaspores. 



In Ulmus americana^ we know that the ''mother cell functions 



s Campbell, Douglas H., The einbr)'o sac of Pandanus. Preliminary note. 

 Annals of Botany 22:330. 1908. 



6 ScHNEGG, H., Beitrage zur Kenntniss der Gattung Gunnera. Flora 90: 161-208. 

 figs. 28, 1902. 



7 Ernst, A., Chromosomereduction, Ent^-icklung des Embryosackes, und 

 Befruchtung bei Paris quadrifolm L. und Trillium grandiflonm SaUsb. Flora 9^ = 



1-46. pis, 1-6, 1902. 



s 



Charles 



BOT. 



Gazette 40:209-223. pis. y-g, 1905. 



