290 REV. PEOE. G. HENSLOW ON THE [Aug. 1907, 



in the Pacific-Coast forest between latitudes 60° and 43° S., but 

 especially south of 51°, as described by Dr. A. F. W. Schimper : — 



' [It is] the most luxuriant, if not also the most diversified on the continent. . . . 

 Trees up to 90 metres [262 feet] in height grow within a few feet of one another. 

 The ground is covered by a dense soft carpet of mosses and ferns, frequently of 

 extraordinary size. Wei] -lighted spaces are filled with impenetrable thickets 

 of various shrubs, in which almost tree-forms of Vaccinium, species of Corylus, 

 and Acer circinatiim play the chief part. The forest owes its extraordinary 

 luxuriance to the very abundant atmospheric precipitations which fall, parti- 

 cularly in winter, and the amount of which (200 cm. and more [=80 inches]) 

 is attained at only a few other places in the temperate zones. The vegetative 

 season is cool, but of relatively long duration. The soil is a porous gravel, 

 only a few inches deep, and of glacial origin.' x 



With regard to the origin of the deep-seated existing coal-fields, 

 I would suggest the following interpretation. 



It is acknowledged that the Carboniferous Period was, on the 

 whole, a quiescent one, so that plants grew undisturbed for un- 

 known ages and formed dense forests on the higher land, while 

 Equisetales especially flourished in the marshes. 



At the close of Palaeozoic times, it is recognized that an epoch of 

 great telluric disturbance supervened, involving contractions with 

 the usual crumpling and faulting. We are quite justified in be- 

 lieving that the Earth's crust began slowly to contract during 

 the epoch of the Coal-Measures. The commencement of shallow 

 grooves would mark the lines of depression, in which those portions 

 of forests (whether upland or lowland) would sink. Water finding 

 its way into the grooves with sand, more or less filled them up, form- 

 ing a new surface for a second forest to grow upon. The spores and 

 seeds for this would be supplied by the persistent upland forests, 

 which continued to grow on either side of the grooves, now left as 

 anticlinal ridges. 



This idea of the sea bringing in the materials for covering the 

 forest seems borne out by Mr. James Lomax's observations on ' The 

 Occurrence of the Nodular Concretions (Coal-Balls) in the Lower 

 Coal-Measures.' 2 He says : — 



' As we all know, there is only one seam of coal in which we find these 

 nodular concretions. . . . Where it is found, in nearly all cases the roof con- 

 tains similar concretions, with this exception — that the fossil remains contained 

 therein are of marine origin, while those found in the coal underneath are 

 always of vegetable origin.' 



This seems to show that the calcium-carbonate, silica, and perhaps 

 iron-pyrites, were derived from sea-water, and that the concretions 

 were formed around fragments of vegetation in the coal below, 

 the superficial layer only containing marine organisms. 



1 'Plant-Geography' [transl. Fisher] 1903. pp. 566-68. 



2 'Annals of Botany ' vol. xvi (1902) p. 603. 



