Floristik, Geographie, Systematik etc. 303 



lying Islands of New Zealand. (Ann. of Bot. XXXI. p. 327 — 

 333. 1 text fig. 1917.) 



This paper is supplementary to J. C. Willis, Ann. of Bot. Vol. 

 XXX, 1916, p. 437. The distribution in New Zealand of the plants 

 which also reach the outlying islands is here dealt with. On the 

 Age and Area hypothesis the preduction is made that the most 

 widespread plants in New Zealand will be those that reach the 

 islands also, and that those which do not reach them will be less 

 widespread. This preduction is confirmed by the facts, both in the 

 case of the wides and endemics. 



It is shown incidentally that submergence raay overtake spread, 

 even to the extent of killing out a species. 



Agnes Arber (Cambridge). 



Yapp, R. H„ D. Johns and O. T. Jones. The Salt Marshes 

 of the Dovey Estuary. (Journ. of Ecology. IV. p. 24—42. 3 

 figs. 1916, and V. p. 65—103. 5 pl. and 13 figs. 1914.) 



The tidal estuary of the river Dovey, near Aberystwyth 

 (Wales) includes a series of plant associations ranging from coastal 

 to moorland. The geological history in considerable detail (by 

 O. T. Jones) is an essential part of the paper, because the present 

 Vegetation can only be understood with reference to the more recent 

 geological changes. The existing Dovey estuary is probably part 

 of a much larger estuarine area which has been curtailed since the 

 Glacial Period by erosion and subsidence. The limit towards the sea 

 is mainly a shingle or storm beach with a leeward belt of blown 

 sand. A submerged forest on clay on the foreshore indicates con- 

 siderable subsidence. On the landwardside, the deposits are mud 

 and sand, alluvium, and peat intersected by the river Dovery and 

 a series of smaller streams, which by erosion and deposition bring 

 about changes in substratum and Vegetation. The Vegetation de- 

 scribed (R. H. Yapp) is mainly that consisting of a) moorland, 

 b) salt marshes. The moorland includes Sphagnetum, Callunetum, 

 and Eriophoretum. A rock outcrop in the peat bears a limited Be- 

 tuletwn with its associates. Surrounding the moorland is a belt of 

 marginal associations mainly Molinetiim and Juncetum maritimi. 



Part II (V. 1914) is a study of the salt marshes carried out in 

 considerable detail, and amply illustrated by a series of 13 instruc- 

 tive diagrams and 22 very clear photographs. In a few meagre 

 notes it is impossible to indicate all the topics dealt with. There is 

 a well-marked zonation of: 1) Salicornietum europaea (lowest), 2) Gly- 

 cerietum maritimae, 3) Armerietiim maritimae, 4) Festucetum rubrae, 

 5) Juncetum maritimi (highest). The combined vertical ränge of 2 

 to 5 inclusive is less than 1*34 metres, yet this is regarded as of 

 great physiological and distributional importance. The features of 

 the chief species are outlined and illustrated; all are efficient col- 

 lectors and binders of silt. Glyceria maritima is the most important 

 pioneer, it is the first plant on the newer deposits, and it invades 

 the drainage Channels. Pans, or shallow depressions with no defi- 

 nite outlet, are an important feature of these salt marshes, and 

 numerous observations on their evolution and history have been 

 made. The authors distinguish two types of depression pans formed 

 in hollows, also Channel pans formed by the segmentation of drai- 

 nage Channels as a result of invasion by Glyceria, etc. No evidence 

 was found that pans ever originate de novo on a sward-covered 



