18 The Plant World. 



trees in a forest. One instance is particularly noteworthy. A 

 veteran pine was found standing in the open, the ground be- 

 neath littered with cones, and many hanging on the branches. 

 Directly beneath the periphery of the rather broadly spreading 

 crown a well marked band of young pines encircled the tree. 

 The largest number of seedlings had evidently arisen where the 

 seeds had fallen the thickest, with other conditions favorable. 

 At one point in the circle the young trees were much larger and 

 thriftier and stood more densely. Among them could be seen, 

 in a state of decomposition, several mounds of earth, the end of 

 a line of entrenchments made by the little rodent, while no other 

 mounds appeared within the area covered by the band of trees. 

 It is quite probable that the fine young generations of pines owe 

 their existence in no small measure to this successful little 

 mammal. 



Tucson, Arizona. 



NOTE ON PEKLO'S WORK WITH MYCORHIZA. 

 By Benj. C. Gruenberg. 



In a preliminary publication on some studies made with the 

 mycorhizas of Carpinus, Fagus, Alnus and Myrica, * Prof. 

 Peklo announces the isolation of the organisms that give rise to 

 the root tubercles in these plants, although he sees no reason to 

 suppose that other species of fungi may not have similar effects 

 in other localities'. 



Having found the usual hanging-drop method of culture 

 unsuited for the isolation of the fungus in mycorhiza, he resorted 

 to a decoction of the mycoihiza itself as probably containing 

 the materials available for the growth of the fungus. In this 

 way he succeeded in observing the outgiowths of hyphae from 

 the mycelia of mycorhiza sections of Carpinus and of Fagus. 

 The action of the decoction is specific to a considerable degree, 

 that is, foreign fungi do not readily thrive in it. Conidia were 

 produced in about three days. From Carpinus there was fre- 

 quently separated a form of Penicillium (Ciiromyces) resembling 

 the species described by Oudemans as geophilus. From Fagus 



♦Beitrage zur Loesung des Mykonrhizaproblems Ber. der deutschen bot. Ges. 27:239-247. 

 June. 1909. 



