f 



IQ02] CURRENT LITERATURE I'&l 



conidia. The author believes that in such genera as Erysiphe the characters 

 of the germ tubes may be advantageously used in defining the limits of diffi* 

 cult species. In every case the germ tubes showed themselves incapable of 

 nourishing themselves from any nutrient media offered. Their size was 

 limited strictly by the amount of reserve material present in the spore. 

 Different lots of conidia also varied widely in the percentage of germinaiion. 

 Light favors germination and the germ tubes are in many cases positively 

 heliotropic. In many cases also the germ tubes show themselves sensitive to 

 contact stimuli. A considerable series of infection experiments were made, 

 and although the evidence was by no means conclusive many results indicated 

 that in the mildews, as in the rusts, we have numerous cases of physiological 

 species, inhabiting only one host plant, within the limits of the species as at 

 present commonly accepted. Cases are also pointed out in which it seems 

 likely that the ascospores may be capable of infecting a wider series of hosts 

 than can the conidia. The theoretical aspects of the data so obtained are dis- 

 cussed at some length. A further interesting observation of the author is 

 that the little known conidia of Phyllactinia are borne in the ordinary basipetal 

 series and not singly as described by Tulasne. Of theoretical interest further 

 is the suggestion that the development of hyphae and haustoria, which pene- 

 trate to the interior of the host leaf, as described by Palla and Smith, is corre- 

 lated with the degree of hypertrophy produced by haustoria in the epidermal 

 cells of the host. The haustoria restrict themselves to the epidermis in cases 

 like Sphaerotheca, in which the cells of the latter are hypertrophied, and 

 thus ( ?) produce an abundant food supply for the parasite. — R. A. Harper. 



Recent Contributions to American Phytogeography: the Eastern 



United States.— E. F. Williams (Rhodora 3 : 160-165. 1901) makes a com- 

 parison of Mounts Washington and Ktaadn, finding general similarity. 

 Mount Ktaadn, however, has a more rugged and arctic aspect, the timber 

 line being exceedingly low; an interesting colony of lowland plants was 

 found well up toward the summit.— J. W. Harshberger (Plant World 5 : 

 21-28. rgo2) gives a brief ecological account of Mount Ktaadn, in which the 

 lowland timber areas are also described.— C. D. HowE (Science 15:462. 

 1902) gives a preliminary account of his studies on a delta plain in Vermont ; 

 the development of the vegetation is traced from the beach, through the 

 Pinus rigida stage, to the culminating forest of beech and maple. The life 

 history in Vermont is found to be essentially like that in Michigan, as worked 

 out by Cowles and Whitford.— C H. Shaw (Bot. Gaz. 33: 437-450- 1902) 

 discusses very suggestively the development of vegetation in morainal 

 depressions near Woods Hole. Physical agents are found to control the 

 filling of ponds in some cases, as evidenced by open marginal belts of water. 

 Euthamia graminifolia flourishes on sandy shores by reason of its running 

 stems; beyond this there are no plants until the depositing zone is passed, 

 where Limnanthemum and other runnerless plants occur. Marginal ditches 



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