Jan., 1906.] Embryo Sac and Embryo of Cueumis sativus. 427 



little deviation (Fig. 27) throughout its entire course; but usu- 

 ally there is a peculiar and characteristic bulging (Fig. 28) some 

 distance above the embryo sac. It spreads out in the surround- 

 ing tissue, completely breaking down the cell structure. How- 

 ever, before it reaches the sac it again narrows, sometimes to a 

 greater extent than elsewhere along its course. After it has 

 pierced the sac it turns to one side or widens out into a foot-like 

 process. 



The most typical tubes have not only a bulging but decided 

 haustoria-like processes (Fig. 29) which extend out into the cell 

 structure of the nucellus and in some cases even break through 

 the inner integument (Fig. 30). The haustorial prolongations 

 appear to act as absorbing and conducting agents for the food 

 material of the embryo. Longo reports to have observed these 

 processes in his study of cucurbita and believes them correlated 

 with the distribution of starch in these parts. He also reports to 

 have found in Cucurbita pepo a conducting tissue which the 

 pollen tube follows from the stigma to the embryo sac. 



The points of especial interest and peculiarity observed in 

 the deveolpment of Cucumis are (1) the long micropyle into 

 which extends the long neck of the flask-shaped nucellus, (2) 

 the presence of two well developed integuments, (3) the anatro- 

 pous ovule with orthotropous embryo, (5) the small size of the 

 embryo sac and associated structures in comparison with the 

 size of the nucellus, (6) the irregular development of the embryo, 

 and (7) the peculiar behavior of the pollen tube. 



The work represented in this paper was carried on under the 

 direction of Prof. John H. Schaifner, to whom I wish to express 

 my sincere thanks for valuable assistance and suggestions. 



PAPERS CITED. 



1. Longo, Be agio, Richerche sulle Cucurbitaceae e il signi- 



ficato del percorso intercellular (endotropic) del tubetto 

 pollinico. R. Accad. der Lincei, 30:523-547 pi. 1-6, 1903. 



2. Longo, Beagio, Osservazioni e ricerche sulla nutrizione dell 



enbrione vegetale. Annali Botanica 2:373-396. 1905. 



3. KiRKWooD, Joseph, The Comparative Embryology of the 



Cucurbitaceae. Bull. N. Y. Bot. Gar. 3:313-402. 1905. 



