• Books and Current Literature. 175 



Some of these grew to be over a foot in length and larger in diam- 

 eter than a lead pencil. 



While there is no doubt that no such phenomena would be 

 expected to occur in a normal healthy tree, yet this is not an 

 adequate explanation for their formation. Certain it is that the 

 vitality of the tree had been seriously impaired and it responded 

 to this abnormal condition by a peculiar development of roots. 

 It would seem, too, that such a growth might better be expected 

 in a more humid region and not under semi-arid conditions such 

 as prevail about Austin. This is one of the singular, natural 

 phenomena the reason for which can only be a matter of con- 

 jecture. 



University of Texas. 



BOOKS AND CURRENT LITERATURE. 



A notable contribution to our knowledge of the physiology 

 of bog plants is made by Dachnowski in a paper entitled " Physio- 

 logically Arid Habitats and Drouth Resistance in Plants," 

 which appeared in the Botanical Gazette for May, 1910. The 

 author had already shown that the physiological effect of bog 

 water and bog soil plays a primary role in the determination of 

 the flora that can best succeed in bogs, the conclusion being 

 drawn in part from laboratory experiments in which it was de- 

 monstrated that various plants exhibited marked differences in 

 their power of resistance to the toxic action of the substratum 

 in question, which thus becomes a definite factor in determining 

 both the character and distribution of plants in such a habitat. 



In the present paper the character and development of 

 drouth resistance in bog plants has been made the subject of 

 extended experimental study, and the data accumulated and 

 conclusions drawn throw light on what has heretofore proven 

 an extrem.ely bafiiing problem. Dr. Dachnowski shows, con- 

 clusively it would seem, that drouth resistance involves a 

 specific reaction on the part of the plant to more than one factor 

 of the physical and biotic environment, and that such resistance 

 in physiologically arid habitats is due to a specific protective 

 functional root activity. Cultures of isolated bog bacteria show 

 that the injurious products of the bacterial bog flora accumulat- 



