1885 it amounted to $688,813 ; i'"^ ^^95 $1,749,070; an increase of 

 153'/^.* But with this development in the methods and extent of 

 greenhouse work there has been a corresponding increase in those 

 elements and factors conspiring to make the success of such work 

 difficult and uncertain. 



All plants growing in the greenhouse in winter are, and must be, in 

 an environment which is in a general way the more or less successful 

 result of an attempt to imitate the natural conditions which exist in 

 an ideal summer, and the degree of healthy and vigorous growth 

 which the plants attain, and indeed their very existence, depends 

 upon the success of this imitation. To be sure the gardener has an 

 advantage over Nature in his absolute control over the heat and 

 water supply, which are the two principal factors upon which the 

 " ideal " conditions depend, but this advantage may or may not be 

 profitable to him according as he employs it properly or improperly. 



Of the factors upon which plant growth depends the most impor- 

 tant are heat, light, air and water, (both in soil and air), as well as 

 the mechanical and chemical nature of the soil. It might seem 

 then that the proper handling of these factors should result in per- 

 fect success in plant growing, but such is not always the case. There 

 are other factors which may come in and render of no avail the 

 greatest skill and knowledge, which reaches only to this point. Arti- 

 ficial heating, ventilation, watering, fertilizing, etc., may be carried to 

 perfection and still there are certain troubles or diseases which may 

 attack the plants and hinder or entirely prevent their growth. The 

 overcoming of such troubles is one of the most difficult problems of 

 the gardener's art. They may be due to insects. These in the lim- 

 ited area of the greenhouse can usually be easily detected and 

 destroyed. Another and more serious source of trouble lies in the 

 attacks of fungous diseases, blights, mildews, rots, etc., which cause 

 so much injury to plants growing in all situations. The Fungi caus- 

 ing these diseases are plants of low order and microscopic size, 

 living as parasites upon other plants and causing more or less injury 

 to them. They are much more likely to attack sickly or unhealthy 

 plants than those growing vigorously. Their occurrence, therefore, 

 especially in the greenhouse, depends to a considerable extent upon 

 the health of the plants. Aside from insects and fungi, injuries may 



*Census of Mass. 1S95, vol. VI., pt. 2, p. 327. 



