CHLOROPHYLL AND LIGHT INTENSITY. 385 



botanists the name Schistostega osmundacea, has even attained a certain celebrity 

 on this account. It is found distributed throughout the Central European granite 

 and slate mountains, but is only to be met with in clefts of the rocks, caves and 

 similar spots. As a rule it covers the yellow, clayey earth and the decayed and 

 disintegrated pieces of stone which form the soil of these caverns and small 

 grottoes. On looking into the interior of the cave, the background appears quite 

 dark, and an ill-defined twilight only appears to fall from the centre on to the side 

 walls; but on the level floor of the cave innumerable golden-green points of light 

 sparkle and gleam, so that it might be imagined that small emeralds had been 

 scattered over the ground. If we reach curiously into the depth of the grotto to 

 snatch a specimen of the shining objects, and examine the prize in our hand under 

 a bright light, we can scarcely believe our eyes, for there is nothing else but dull 

 lustreless earth and damp, mouldering bits of stone of a yellowish-grey colour. 

 Only on looking closer will it be noticed that the soil and stones are studded and 

 spun over in parts with dull green dots and delicate threads, and that, moreover, 

 there appears a delicate filigree of tiny moss-plants rising star-like, pale bluish- 

 green in colour, and resembling a small arched feather stuck in the ground. This 

 phenomenon, that an object should only shine in dark rocky clefts, and immediately 

 lose its brilliance when it is brought into the bright daylight, is so surprising that 

 one can easily understand how the legends have arisen of fantastic gnomes, and 

 cave-inhabiting goblins who allow the covetous sons of earth to gaze on the gold 

 and precious stones, but prepare the bitter disappointment for the seeker of the 

 enchanted treasure; that, when he empties out the treasure which he has hastily 

 raked together in the cave, he sees roll out of the sacks, not glittering jewels, but 

 only common earth. 



It has been mentioned that on the floor of rocky caves one may discern by 

 careful examination two kinds of insignificant-looking plant-structures, one a web 

 of threads studded with small crumbling bodies, and the other bluish-green moss- 

 plants resembling tiny feathers. The threads form the so-called protonema, and 

 the green moss-plants grow up as a second generation from this protonema. How 

 this comes about will be described in another place; here it only interests us that 

 the gleams do not issue from the green moss-plants, but only from their protonema. 

 If this is viewed under the microscope a sight is presented like that depicted in 

 fig. 25a, p. From the much-branched threads, composed of tubular cells, which 

 spread horizontally over the ground, numerous twigs rise up vertically, bearing 

 groups of spherical cells arranged like bunches of grapes. All the cells of a group 

 lie in one plane, and each of these planes is at right angles to the rays of light 

 entering through the aperture of the rocky cleft. The grape-like groups of cells 

 have longer or shorter stalks, but they always appear in rows side by side and 

 behind one another, placed cup-like, that the anterior groups do not deprive those 

 behind them of too much of the light which enters the cavity. Each of the 

 spherical cells contains chlorophyll -granules, but in small number; usually four, 

 six, eight, or ten and they are always collected together on those sides of the 



