189 



OBSEEVATIONS upon the POLLEN TUBE. 

 By A. J. Ewart, B.Sc. 



1851 EXHIBITION SCHOLAR. LATE DEMONSTRATOR OF BOTANY IN 

 UNIVERSITY COLLEGE, LIVERPOOL. 



With Plate XL 



[Read 14th December, 1894.] 



The following paper gives the results of an investigation 

 on certain points in connection with the pollen tube, 

 which was suggested to me by Professor Keynolds Green, 

 F.K.S. Whilst investigating the zymogenic activity of 

 the developing pollen tube Professor Green came to the 

 conclusion that the enzyme was excreted from the apex 

 of the tube in the form of solid particles of zymogen, 

 and certain appearances seen in the pollen tubes of 

 Narcissus led him to infer the presence of a definite and 

 permanent excreting pore in the apex of the pollen tube. 

 At his suggestion I attempted to determine the nature of 

 this pore and whether its presence was a constant and 

 normal feature of the pollen tube. 



On examining the apices of stained and mounted pollen 

 tubes, under high powers ( T V immersion) a few on each 

 slide were seen to shew very minute terminal oval or 

 rounded pores and in some cases a small amount of gran- 

 ular material which had evidently been extruded by the 

 tube through the pore could be seen still adhering to the 

 outer surface of the apex of the pollen tube. These pores 

 could be satisfactorily distinguished only in normal pollen 

 tubes of Narcissus, Tulipa, Lilium and Scilla though the 

 apices of the pollen tubes of several other plants, Lathyrus, 

 Brassica, Cheiranthus, Vacciniuvi, Mercurialis, etc., were 

 similarly examined. The question which needs to be 

 answered is whether this pore is permanent and the path 



