686 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



tioii involving much more than the really injured cells. If this process 

 removes a large portion of the lamina, the whole leaf drops." — B. N. 



Cronartium ribicola on Pines. 



Cronartium ribicola. By P. Magnus (Not. Konig. Bot. Berlin, 

 Vol. iii. (1902), p. 183). — Klebahn in 1888 showed that Peridermium 

 Strobi, Kleb., is the aecidium of this uredine, and that it occurs on Pinus 

 Lambertiana, Dougl., as well as on P. monticola, Dougl., and in 1890 the 

 same observer suggested that it also lives on P. Cembra, L. This has 

 now been confirmed by Tranzschel in Russia, who has infected Bibes 

 nigrum with the spores of the Peridermium from P. Cembra, L. 



Magnus remarks that Henning's doubt whether Pinus Strobus can 

 have been the means of infecting the species of Bibes referred to in Not. 

 Konig. Bot. Berlin, No. 28 (see Journal R.H.S., Vol. xxvii. (1902), 

 p. 236), is unnecessary, since that Pine and its Peridermium often occur 

 near Berlin, and re-infect the Bibes annually. Magnus regards it as 

 probable that various local races of the Cronartium occur. — H. M. W. 



Vegetation Destroying Ponds. 



Development of Vegetation in the Mopainal Depressions of 

 the Vicinity of Wood's Hole, Mass. By C. H. Shaw (Bot. Gaz. 

 xxxiii. No. 6, p. 437). — The depressions occur in a terminal moraine of 

 clay, sand, and boulders. They are known as " kettle-holes," in which 

 ponds and lakes are formed, each one the first term of a long series 

 ending in its own obliteration. 



The author first remarks upon the physical causes of obliteration, the 

 intrusion after severe storms being often very great, while rain-rivulets 

 make small deltas, upon which the yellow-flowered Gratiola aurea soon 

 becomes conspicuous and characteristic. 



The vegetation is distributed in two zones. Limnanthcmum lacu- 

 nosum forms a continuous belt, but never touches the shore. Lobelia 

 Dortmanna is in the same zone, growing entirely submerged, its flowering 

 stems being unable to reach the surface. On the shore-line, separated 

 from the above by a zone of clear water, is Euthamia (Solidago) gramini- 

 folia. The shoreward limit of the previous zone was set by the action in 

 the shallow water of the wavelets in shifting the silt and burying the 

 bottom-growing vegetation. 



Euthamia resists burial by possessing running stems penetrating the 

 sand in all directions. The others have no runners, and so are driven to 

 the deeper zone beyond. 



Floating vegetation assists in the destruction of the pool. This is 

 effected by the increase of such plants as Water-lilies in the body of the 

 pool till a footing is afforded for the less anchored forms, and the con- 

 sequent formation of the floating mat vegetation. Several species of 

 Utricularia aid greatly by means of their floating and branching tufts. 

 Then Sphagnum and other Mosses, Carices, Xyris, and Drosera appear. 

 In some Decodon (Nesaa) verticillatum (Lythrariece) plays a leading part. 

 In others Hypericum borcale takes its place. Its submerged stem is an 

 unbranehed axis, weak and slender ; but on reaching the surface it breaks 



