THE PAGE OF NATUJtE. 147 



The actinic power of the solar light, aided by some pecu- 

 liar, and as yet unknown property belonging to the natu- 

 ral whiteness of the snow itself, is highly essential in the 

 production of the beautiful crimson or rose colour, by 

 which the red snow is distinguished ; but this colour, as 

 in the case of the varieties mentioned above, gradually 

 changes to green when secluded from the direct action 

 of light, and developed on dark or opaque objects. 



Another extremely curious plant closely allied to the red 

 snow is ihePalmella cruenta (Fig. 21) or Gory Dew. Like 

 the Protococcus it consists of a number of aggregated 

 globose cells, forming a very thin crust-like frond of a 

 dark blood colour. Each of the cells divides first into 

 two, then into four parts, each capable of propagating 

 the plant. It grows on damp limestone in the open air, 

 or on whitewashed walls, particularly in cellars, and the 

 mouldering rooms of old neglected buildings, and figures 

 largely in the history of the superstitions of the middle 

 ages. Pitarello, a peasant residing at Legnaro, near 

 Padua, observed large patches of it covering the walls of 

 an old and rarely visited room in his house, which so 

 closely resembled huge clots of venous blood, that the 

 greatest curiosity and consternation were excited. The 

 streets of Padua leading to Legnaro were thronged by 

 anxious crowds hastening to inspect the phenomenon, and 

 full of the calamities it foreboded. Many regarded it as 

 a direct judgment of God upon the unhappy peasant, for 

 having forestalled corn during the famine. During the 

 last invasion of epidemic cholera, thesame plant was found 

 in abundance, purpling the ground near Oxford, as if red 

 wine or blood had been poured out. 



