Vol. 33 



BULLETIN 



No. 6 



OF THE 



TORREY BOTANICAL CLUB 



JUNE, 1906 



infl 



The pollen-tube in some of the Cucurbitaceae * 



Joseph Edward Kirkwood 



(WITH PLATES l6 AND 17) 



In a previous paper on the embryology of the Cucurbitaceae " 



it was the writer's intention to deal with the matters suggested in 



the present title, but lack of evidence on certain points, and other 



causes, necessitated their omission at that time. It is hoped here 



to discover some of the controlling factors in the behavior of the 



pollen-tube in Mclothria, Micrampelis and Cyclanthera, one species 

 of each. 



The various phases of the development of the pollen-tube have 

 been studied by numerous writers in widely differing subjects, but 

 until recently little has been done to determine the nature of the 



uence which directs the pollen-tube in its growth. The con- 

 clusions, however, based upon anatomical and experimental evi- 

 dence, have been by no means unanimous, and much still remains 

 to be done in this field of investigation. 



The behavior of the pollen-tube has been seen to vary considera- 

 bly in different groups. The manner in which it approaches the 

 embryo-sac in different cases has led Pirotta and Longo 27 to rec- 

 ognize three distinct conditions : acrogamy, in which the pollen- 

 tube enters the micropyle, a condition obtaining in the majority of 

 seed plants ; basigamy, including those cases in which the tube 

 enters by way of the chalaza, occurring in the Amentiferae ; and 

 mesogamy, which thus far has been found in a few cases only and 

 applies to those instances in which the tube enters the nucellusby 



This work was done on a research scholarship at the New York Botanical Gar- 

 den, m the summer of 1904. The writer desires to acknowledge with thanks the kind- 

 ness and cooperation of the officials of that institution. 



[The Bulletin for May, 1906 (33 : 271-325,//. 12-13) was issued 13 Je 1906.] 



327 



