NOTES ON EECENT EESEARCH. 



237 



After giving evidence that this fungus does not form a perennial 

 mycelium in these Currants, and observing that the Peridermium is 

 absent from the Pines near the Dahlemer Garden, he urges the signifi- 

 cance for plant pathology of the fact that the Cronartium nevertheless 

 attacks, and maintains itself on, various species of Bibes of the sections 

 Ribesia, Grossularia, and Siphocalyx, e.g. on Bibes nigrum var. ketero- 

 phyllum, B. bracteosum, B. multiflorum, B. petrceum, B. americanum, 

 B, rubrum, B. floridum, B. sanguineum, B. Gordonianum, B. aureum 

 var. leiobotrys, B. tenuiflorum, B. Grossularia, B. Cynobasti, B. aciculare, 

 B. sctosum, B. oxycanthoides, B. subvestitum, B. triste, B. rotundifolium, 

 R. hirtellum, R. divaricatum, B. niveum, B. irriguum, B. triflorum, B. 

 prostratum. On some of these the fungus is observed for the first time. 



Hennings regards the explanation of the fact that the Cronartium 

 affects the leaves of different species in different degrees as depending on 

 the varying texture, hairiness, &c. of the leaves ; but in view of the 

 recent experiments, which show clearly that the relative immunity from, 

 or predisposition to, epidemics of rust-fungi is independent of the 

 anatomical structure of the grass-leaves concerned, it would seem that 

 this view of Hennings needs critical and experimental investigation. 



H. M. W. 



Ecology. 



Ecological Relations of the Vegetation of W. Texas. By 



W. L. Bray (Bot. Gaz. xxxii. No. 2, p. 99 ; No. 3, p. 195 ; No. 4, p. 262). 

 This valuable paper, extending through three numbers, contains plans 

 and photos. First dealing with temperatures over the numerous subdivi- 

 sions of the country, he points out that while in the south, on the coast, 

 it is tropical, in the north, latitude 32°, there are mountains 9,000 feet in 

 height, and in the extreme north, an elevation of 5,000 feet, so that the 

 extremes of a continental climate exist. 



With regard to the rainfall, beginning with an average of 30 inches at 

 the 98th meridian, that at the west decreases to 9 inches. The organisa- 

 tion of vegetation with respect to moisture emphasises the zones of 

 precipitation into which the State may be divided, the result being a 

 complete transition from the mesophytic flora on the east to the intensely 

 xerophytic one on the west. Thus Juglans nigra is succeeded by J. 

 rupestris, and Juniperus virginiana by sabinoides. 



The next point is the prevalent direction of wind, the heated plains 

 being an efficient cause of strong breezes. Their significance is (1) in 

 their mechanical impact ; (2) in rapid evaporation ; (3) in erosion and 

 transportation of soils ; (4) in their humidity. 



With reference to light its effect in Texas is seen upon the general 

 dwarfing of the vegetation and in the "orchard tree" type of trees. 

 Experiments made with Maize showed that grain sown in Texas produced 

 a much shorter stalk than the same variety in New York. " The sun's 

 rays are almost at the maximum intensity during the vegetative season, 

 and their intensity is undiminished by atmospheric moisture." 



Plant Formations. — These are included in (1) grass, (2) woody, 

 (3) succulent, (4) rocks, (5) halophytic. The first is most prominent, as 



