MISSOURI BOTANICAL GARDEN. 



of humus increasing in width (c). In drying, numerous 

 fissures have appeared in the mass. The lignin layer be- 

 comes narrower and narrower, then disappears and at last 

 even the primary lamella no longer gives the lignin reaction, 

 and the whole is transformed into humus compound (e). 

 The positions of the original cells are still very evident, 

 and here and there a piece (u) of unchanged cell- wall re- 

 mains in the homogeneous mass of matter. 



The action of the rotted membranes on polarized light 

 has already been mentioned. The primary lamella shows 

 decided light lines in a transection of the kind shown on 

 PL 3, fig. 2, but as soon as the wood no longer gives the 

 lignin reaction it appears dark when the Mcol prisms are 

 crossed. The same is true of the humus compound. 

 Whatever the change is which changes a non-homogeneous 

 body to a homogeneous one, it is one which takes place 

 when the chemical structure of the non-homogeneous body 

 begins to change. When a portion of the humus mass is 

 dissolved in dilute KOH there appear in the center of this 

 mass certain highly refractive bodies -J- 1^ p in diameter, 

 of very definite structure resembling human blood corpus- 

 cles somewhat (PL 5, fig. 8). They are hexagonal in 

 shape with blunted corners and have a much depressed 

 center, so that the edge view shows four contour lines, two 

 parallel lines, and two of an hour-glass shape. When exam- 

 ined with polarized light they shine brightly when viewed 

 from the edge, and as they have a decided Brownian 

 motion, they alternately flash and disappear. Their very 

 variable size, but constant form, as well as their appearance 

 in polarized light, suggest that they are crystals of some 

 sort. Hartig * says that the comparatively high resistance 

 of the walls bounding the lens-shaped pits, is probably due 

 to the large number of calcium oxalate crystals imbedded in 

 these walls; he indicates these by fine dots (fig. 13). The 



* Hartig, R. Der achte Hausschwamm 57 

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