192 



The Plant World. 



The lichens of the Desert Laboratory domain were collected 

 at seven stations, and in certain cases, which are discussed at 

 length, are seen to exhibit marked differences referable to sub- 

 stratum on the one hand and aspect on the other. Among other 

 conclusions based on com arative study of habitats here and in 

 Minnesota, the author states that species of Acarospora, with 

 their strong protective cortices and cellular structure throughout, 

 are the most characteristic xerophytes of all our American lichens 

 thus far studied from the ecologic point of view. 



In the discussion of lichen distribution as influenced by 

 moisture and air movements the author considers at length the 

 evidence thus far obtained regarding absorption of moisture by 

 lichen thalli from the atmosphere and also from the substratum, 

 and assumes, until otherwise proven, that lichens absorb at 

 least a large proportion of the moisture needed directly from 

 water vapor of the atmosphere and from water falling upon them. 

 He attributes to drying southerly winds an influence accentuat- 

 ing the effect of direct sunlight, thus leaving the northward 

 facing ledges by far the best habitats for lichens. 



The value of the paper, as should be the case in contribu- 

 tions of this nature, consists not merely in its presentation of data 

 and conclusions, but also in the pointing out of promising fields 

 of investigation suggested in the course of the work thus far 

 accomplished. In conclusion it may be said that had the author 

 limited his study to a determination and enumeration of the spec- 

 ies of desert lichens which were sent to him for examination, he 

 doubtless would have contributed to the advancement of botani- 

 cal science, but very few persons would have cared, nor does 

 any reason appear why thev should. 



Tropical Life announces a prize of fifty pounds sterling for 

 an essay embodying research work directed towards ascertain- 

 ing "exactly what changes (together with their causes and 

 whether these changes occur during the fermentation process 

 only or while being dried) take place in the cacao bean between 

 the time that it leaves the pod until it is shoveled into the bag 

 for export." For further information those interested may 

 address the editor of Tropical Life, 112 Fenchurch St., E. C, 

 London. 



