366 INDEX. 



Beautiful adaptation of the atmosphere to plants and animals, — Effect of 

 pure oxygen. — Property of watery vapor in vegetable economy. — Subtlety of 

 the air. — Necessity of maintaining au adequate supply of aqueous vapor in the 

 atmosphere. — Instruments for guiding us in regulating the atmosphere. — In- 

 struments much wanted for measuring the respective quantities of the gaseous 

 elements, 305 



SECTION VI. 



PROTECTION OF PLANT-HOUSES DURING COLD 



NIGHTS. 



Advantages of protecting bodies. — Conditions of the plants at low temper- 

 atures. — Light coverings otherwise useful. — Experiments on the cooling 

 effects of wind. — Materials for protecting glazed structures. — Methods of 

 protection, 309 



Slight covering that is required to protect plants from frost. — Experiments 

 of Dr. Wells on coverings. — Method of covering. — Distance to keep the cov- 

 ering from the object protected, ... 313 



Effects of vertical coverings. — Horizontal coverings. — Coverings of straw, 

 etc. — Protection afforded by walls. — Protection of snow. — Warmth afforded 

 by the soil to trees in winter, 317 



SECTION VII. 



GENERAL REMARKS ON THE MANAGEMENT OF 

 THE ATJIOSPHERE OF HOT-HOUSES. 



Adjustment of the artificial to the natural atmosphere. — Observations of 

 Knight. — Rest necessary to plants during night. — Cause of the imperfect 

 maturation of fruit-tree blossoms. — High night temperatures exhaust tne ex- 

 citability of the trees. — Plants continue longer in bloom in low night temper- 

 atures. — Admission of external air during day. — Difference of climate be- 

 tween this country and England, 320 



Rules to be observed by the gardener in charge of hot-houses. — Dutch meth- 

 od of forcing. — Excessive moisture — its effects. — Necessity for pei-iods of 

 rest to plants. — Changing the period of fructification, 325 



SECTION VIII. 



VENTILATION WITH FANS. 



. Construction of ventilating fans. — Methods of using them. — Their adapta- 

 tion to horticultural purposes. — Different kinds of fans. — Objects to be ef- 

 fected by them. — Requisites to the use of fans. — Windmill ventilators. — 

 Their employment in horticultural buildings. — Pun p ventilators. — Ventila- 

 tion by means of chimney shafts, &c 329 



