278 THE PLANT WORLD 



bers of the earlier aspects and a uniform distribution for 

 those of the later ones. The members of the successive as- 

 pects overtop those of the earlier ones. The slopes facing 

 north are the most mesophytic upland habitats, and on them 

 occur a sod of Poa prateusis and the only shrubs of the for- 

 mation, — RJiiis glabra and Symphoricarpos occidentalis, 

 which are succeeded by Oiierciis macrocarpa and Uhniis fulva 

 in the encroachment of the mesophytic element upon that 

 of the prairie. 



As the result of an extended investigation conducted in 

 Pfeffer's institute Zehl, L., finds that at a given concentra- 

 tion of poisonous solutions their toxicity is greatly increased 

 with rise of temperature, in most cases finally becoming 

 three-fold what it was at the outset. Germination of spores 

 of AspergiUus and PeniciUium was employed as a test of 

 concentration. Of the few exceptions to the general rule 

 chloroform and ether show a marked falling off in toxic 

 action with increase of temperature. 



Schiller, J., who has studied the local distribution of 

 Ceramiiim radiciilosiim in streams tributary to the Gulf of 

 Triest, has ascertained that this species advances up stream 

 as far as the water becomes brackish at flood-tide and as far 

 down stream as fresh water reaches at ebb-tide. In other 

 words the plant grows where every 24 hours it is twice im- 

 mersed in fresh, or decidedly freshened water and the same 

 number of timies in salt or strongly brackish water. The same 

 factor is potent also in its vertical distribution. It does not 

 live in water containing one and seven tenths per cent, of 

 salt. It attains its best development at a depth of 0.6 m. to 

 1.2 m., and does not occur at a depth of 2 m., that is its 

 lower vertical limit is reached where very salty layers of 

 water predominate. 



Gilg has recently published an extended study of the 

 relationships and distribution of the American species of 



