492 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



and, as already pointed oat, the winds prevailing in a valley must 

 bring distinct conditions, which ought always to be considered. Moun- 

 tains and valleys are thus routes of migration for plants, because 

 somewhere, high or low on the slopes, any given species can find those 

 conditions best suited for its full development and reproduction. Thus 

 to many plants the Danube plain would be a complete barrier, but the 

 fact that the Carpathians come down to and cross the Danube opens a 

 way for exchange between north and south. A long simple mountain 

 range without lateral spurs or broad intersecting valleys is well adapted 

 to act as a bridge for migration, but the number of species will prob- 

 ably be small because the slopes are everywhere exposed. The con- 

 ditions on a mountain " massif " are different, spurs branch off in 

 many directions, thus affording much variety in exposure and shelter, 

 and favouring a greater number of species. The mass is also less! 

 liable to extreme climatic conditions, and in Servia the presence of;' 

 grouped mountains furnishes the lower lands with moisture, an import- f 

 ant item in a region with summer drought; a longer winter also! 

 results, but this furnishes conditions suitable for the growth of species j 

 requiring moisture and a cool climate. The author also confirms an 

 important conclusion in phytogeography, namely that in a great 

 "massif" all the zonal limits of plants are lifted upwards. Thisi 

 means, using local examples, that a tree-limit of 2000 feet may be! 

 expected in the heart of the Grampians where altitudes of 3000 feet arej 

 common, but on long simple ranges like the Sidlaws and Pentlands' 

 where the higher altitudes are about 2000 feet, the possible tree-limit u 

 not more than about 1500 feet. In the same way, the cultivation oi 

 crops is actually carried higher in the Perthshire " massif " than it is! 

 on the long open ranges. Dr. Adamovid attributes this to wind more 

 than to temperature or soil. The higher and more complex the moun^ 

 tain group, then so much higher lies the most destructive sphere of the 

 wind ; hence there is for plants a greater area available with a favour- 

 able environment, including suitable insolation, soil-warmth, and soil 

 moisture. The "'massif " also tells in another way. On a narrovl 

 range with peaked summits, narrow ridges and steep broken slopes, thfj 

 atmospheric agents which effect weatliering and erosion have full play, 

 hence screes of talus and wind-swept rocky slopes occupy a large proi 

 portion of the ground and are unsuitable for a large plant populationj 

 On the " massif " all this is modified, and a greater part of the arejj 

 consists of rounded summits with broad intervening cols and gentLj 

 slopes completely clad with grassland, moor or forest. Here erosion 

 has less effect, the soil is less disturbed, and the primitive vegetatioi 

 remains, whereas on recently disturbed soil only a few relict specie 

 can retain their place and a number of new-comers find a home. 



A considerable part of the memoir deals in detail with the forma 

 tions constituting the vegetation, but a passing glance at a few of th 

 more noteworthy must suffice. The most important forest of thj 

 Mediterranean part of the area is that of the Flowering or Manna As| 

 [Fraxmus Oiiiua). This tree forms the chief element in a somewhf! 



