abstracts: botany 493 



BOTANY. — A remarkable new fern from Panama. William R. Maxon. 



Smithsonian Miscellaneous Collection 56: no. 24. Pp. 1-5, with 



3 plates. November 22, 1911. 



A description of Polypodium podocarpum, a new species from the 



Cordillera of Chiriqui. This plant is unusual for the genus in having 



fronds of indeterminate growth and the sori borne at the apices of lobes 



of the pinnae. Its morphology is otherwise peculiar. 



P. C. Standley. 



BOTANY. — Maturation artificieUe lente de la datte Deglet-nour. Wal- 

 ter T. Swingle. Comptes Rendus 155: 549-552, no. 12. Sep- 

 tember 16, 1912. 



Deglet Noor date palms from Algeria, introduced into Arizona and 

 California in 1900, have never properly ripened their fruit on the tree 

 although the total heat in some parts of these states exceeded that neces- 

 sary for the ripening of this date in the Algerian Sahara. 



A satisfactory method of artificial ripening is therefore necessary. 

 Slow artificial ripening at a low temperature gives much better results 

 than any chemical means hitherto employed, and is perhaps still more 

 important than the incubation system used by Prof. George F. Freeman 

 of the University of Arizona. 



Attention was first called to this new method by the transformation 

 of unripe, yellowish, bitter fruits into delicious, amber-colored, trans- 

 lucent dates within ten days. These dates were in a valise and remained 

 at a temperature of 20° to 30° C. in hotels or sleeping cars during a trip 

 from Mecca, California, to Washington, D. C. 



As it seemed probable that the slow ripening which had taken place 

 in the valise is similar to that which takes place in the boxes of dates 

 shipped from the Algerian or Tunisian Sahara to Biskra and Marseilles 

 for packing and exportation, opportunity to investigate this question 

 was taken on a trip to Africa in December, 1911. As a matter of fact, 

 most of the dates in the boxes shipped from the Sahara are ripened by 

 this slow process to which, however, no attention has ever been given. 



Date ripening is composed of two distinct phases — the botanical 

 ripening in which the fruit attains its size and has a ripe seed, and the 

 true ripening during which the cane sugar becomes inverted sugar 

 and the diffused tannin is deposited in insoluble form in the giant cells. 



While the important factor in botanical ripening is heat, humidity 

 is essential for true ripening. The air surrounding the fruit must be 

 saturated by the moisture given off by the dates as they dry and become 



