VEGETABLE LAMPS. 129 



The southern oceans, in certain places, often swarm with 

 these minute light-givers, and when borne aloft in the spout, 

 they tend to produce one of the most remarkable and strik- 

 ing scenes possible to imagine. In color these luminous 

 columns are yellow, of different shades, according to the 

 numbers of diatoms present. The naturalists of the " Chal- 

 lenger" found that P. pseudo-noctiluca was always present, 

 and often existed at the surface in vast numbers, in the 

 tropics and subtropical regions where -the temperature was 

 over sixty-eight or seventy degrees ; and the most beautiful 

 exhibitions seen during the cruise were due to these little 

 forms. They have been observed in the Bay of Funchal all 

 the year round. The light was equally brilliant in each 

 species ; and in each, when disturbed several times in suc- 

 cession, the phosphorescence perceptibly diminished, and 

 finally disappeared ; but after an hour's rest, it re-appea-red 

 as brilliant as before. 



The phosphorescence of plants, though not so remarkable 

 in its general manifestations as in the forms previously 

 reviewed, is sufficiently interesting to attract general atten- 

 tion. In nearly all countries these vegetable lamps are 

 found ; and even in the old legends of the Greeks, Hindus, 

 and Persians, references to the "burning bush," and other 

 luminous phenomena are met with, evidently having some 

 foundation in fact. In India the old natives tell the story, 

 that their forefathers, who visited the mountain of Sufed 

 Koh, at the north of Nalroo in Afghanistan, found a spring 

 in which grew a bush which, from a distance, seemed to 

 emit a brilliant light ; but if any one approached, it imme- 

 diately disappeared, vanishing in the air. In 1845 the white 

 residents of Simla were informed by the natives that a won- 



