280 



thold and Russow. In all the experiments tried, it is claimed 

 that the substance of these walls, In both chemical and physical 

 action, appeared entirely unlike protoplasm. 



In regard to their biology, he concludes that this is a special 

 arrangement for the preservation of the species. This appears 

 from the fact that the ordinary wall allows these oils to escape 

 very easily. Examples are given where volatile oils escape with 

 great rapidity through the ordinary walls when the fruit first be- 

 comes dry. It is well known that the fruits of the Umbelliferse 

 such as fennel and caraway seeds, as we call them, retain their 

 pungent aromatic odor for a long time, which he claims would be 

 quite impossible were it not for the protection afforded the oil 

 by the suberous nature of the walls in which it is held. Again 

 it is also well known that the oil of these plants has an injurious 

 effect on many insects, birds, etc., when eaten by them. There- 

 fore these suberous walls must be regarded as a special arrange- 

 ment for the preservation of the species. E. L. G. 



Index to Recent American Botanical Literature. 



Acacia flexicauUs. C. S. Sargent. (Garden and Forest, ii. 400, 

 %. 123). 



Aigcz~The Fresh Water— and their Relation to the Parity of 

 Public Water Supplies. Geo. W. Rafter. (Eng. and Build. 

 Rec. XX. 115, 1 16-129, 131)- 



Abstract of a paper read before the Am. Soc. Civ. Eng., 

 May I, 1889. 



Asa Gray. Andrew Taylor. (Trans, and Proc. Edinburgh Bot. 



Soc. xvii. 346-350). 



An obituary notice read before the Edinburgh Bot. Soc, May 

 10, 1888. 



Aster Lindleyanus. (Garden and Forest, ii. 448, Fig. 127). 



This fine species has recently been detected in Mt. Desert by 

 Mr. Rand. 



Bignonia radicaus. L. Greenlee. (Vick's Mag. xii. 270, il- 



lustrated). 



Catalpa and Paulozi'nia~The Leaves of. A. C. Stokes. (Mi- 

 croscope, ix. 225-231). 



