ARE PLANTS INJURIOUS TO HEALTH? 183 



is emitted. Here we meet them by the information that in 

 most cases the gardener in charge of green-houses often 

 has to be up the greater part of the night in winter, and 

 the green-house, from its warmth, is universally taken as 

 his sitting-room, and sometimes as his bed-room ; such 

 was my own experience for three winters. I had charge 

 of a large amount of glass, situated nearly a mile from my 

 boarding-house, too far to go and come at midnight, with 

 the thermometer below zero. Our means of heating were 

 entirely inadequate, so that the fires had to be looked to 

 every three or four hours. Disregarding all my kind- 

 hearted employer's admonitions, I nightly slept on the 

 floor of the hot-house, which was rank with tropical 

 growth. The floor was just the place to inhale the gas, 

 if there had been much to inhale. It did not hurt me, 

 however, and has not yet, and that is a score of years 

 ago. That plants are injurious to health in sleeping- 

 rooms is one of the bugbear assertions that is willingly 

 swallowed by the gullible portion of the community, always 

 ready to assign effects to some tangible cause, and this, as 

 the assertion evinces some chemical lore, is one very prev- 

 alent among those disciples of Esculapius who are 

 always willing to be thought learned in the science so 

 intimately connected with their profession. 



CHAPTER XXVIII. 



NATURE'S LAW OF COLORS. 



It has long been a belief among students in vegetable 

 physiology, that, in certain families of plants, particular 

 colors prevail, and that in no single instance can we ever 

 expect to see blue, yellow ', and scarlet colors in varieties 

 of the same species ; yet, undeviating as this law seems 



