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i6 



THE SPHAGNACE^ OR PEAT-MOSSES OF 



nate, obliquely inclined septa, a leaflet is produced composed of a few 

 large quadrate parenchym cells filled with a slimy fluid containing 

 chlorophyl granules ; but with <•'* ' appearance of the fifth leaflet 

 begins t'le differentiation into two kinds of cells so characteristic of 

 the Sphagnacecc. 



The leaf becomes marked out into a system of square cells, 

 each of which is surrounded by four oblong cells ; in the latter 

 chlorophyl granules rapidly increase in number and size, while the 

 former lose all colouring matter from their contents and keep 

 enlarging at the expense of their protoplasm ; then the fibres are 

 deposited on their internal walls, first as fragmentary rings which 

 afterwards coalesce into complete rings or spirals ; and lastly, 

 small scattered rings appear on the internal surface, the membrane 

 enclosed by which becoming resorbed, there result the well-known 

 pores or foramina so generally present in the branch leaves of these 

 plants, through which it is not uncommon to find infusoria have 

 passed, for we may see them sporting about in the interior of the 

 cell. 



Hedwig had noticed the beautiful structure of the SpJiagnum 

 leaf, for in his Fundamenta Hist. Nat. Muscorum, i. p. 25 (1782), he 

 mentions the large areolae, void of chlorophyl, traversed by very 

 fine vessels containing parenchyma, which he suggests may corre- 

 spond to the ducts of flowering plants, 



Moldenhawer, however, detected the true nature of the areo- 

 lation, and the two kinds of cells of which it is composed, with the 

 presence of threads and pores in the vesicular cells, and Von 

 Mohl still further extended his researches. 



The leaves of all Sphagna consist of a single stratum of cells 

 without any midrib, and these cells are of two distinct kinds 

 alternating with each other : ist, narrow chlorophyllose cells 

 {ductiis intercelhilares of C. Muller, inter stitia of Hampe), which 

 form a frame or network of somewhat bent hexagonal meshes, 

 and usually six of these cells enter more or less into forming the 

 boundary of each mesh, their colour being green, yellow, or red, 

 according to that of their contents ; these cells are really the most 

 important part of the leaf, since they carry on the vital functions, 

 and form the scaffold on which the hyaline cells are stretched : 

 2nd, large colourless vesicular cells dropped as it were into each 

 mesh of the network, and containing in nearly all species spiral 

 fibrils on their internal wall and perforated with foramina; for 



