PROBLEMS TO SOLVE. 385 



Chapter XLIV. Is any lizard on the Riviera 

 unable to endure the midday sun in Summer ? 



Is the phenomenon of aestivation observed in 

 many plants beside Euphorbia dendroides f 



Chapter XLVII. Whence and whither does V. 

 cardui migrate ? 



Chapter XLIX. Has any naturalist given a 

 definite explanation of the " Summer hum" ? 



Chapter LIU. What are " St. John's hairs " ? 



