mildews of various plants grown in the shade are too well known 

 to need consideration. Since plants grow the most in the night, 

 care must be taken to obtain a proper night temperature. Too 

 high a night temperature accelerates growth and results in the 

 formation of a more or less delicate tissue, and under the influ- 

 ence of bright sunshine wilting and often death results. Tissue 

 formed at 45° F. is quite different from that formed at 50° F. 

 as regards susceptibility to disease. The quality and size of glass 

 and the other material used in greenhouse construction affects 

 plant development, and some specific troubles can be traced 

 directly to inferior construction. Crops grown in greenhouses 

 from which 30% to 40^0 of the light is shut out will develop 

 quite differently from those grown in houses where only 10% 

 is shut out. 



A serious wilt affecting cucumbers under glass is frequently 

 observed, and affords a good illustration of trouble resulting from 

 inferior greenhouse construction. 



The regulation of atmospheric moisture is important in con- 

 trolling many fungous diseases. Too much moisture in the house 

 induces mildews and blights. Syringing the plants in bright sun- 

 shine, when the moisture on the foliage will dry off quickly, 

 reduces the chances of infection, whereas when the moisture is 

 allowed to remain on the foliage, as is the case when syringed 

 at night, spore germination will take place and infection result. 

 Diseases caused by Plasmopara, Alternaria and Anthracnose. 

 common to cucumbers and melons in the field, may be completely 

 controlled under glass if attention is given to the regulation 

 of the moisture, and this is also true of tomato Cladosporium, 

 cucumber mildew, chrysanthemum rust, and carnation rust to a 

 large extent. The effect of atmospheric moisture is quite notice- 

 able on outdoor blights, such as the oak (iloeosporiuni, asparagus 

 rust, etc. Asparagus seldom, if ever, rusts when grown in the 

 shade of trees, and oak Gloeosporium is usually confined to the 

 sides of trees which are shaded. 



The circulation of air also has a marked effect on the develop- 

 ment of resistant tissue in greenhouse crops, and a lack of it is 

 responsible for many leaf blights and rots. Even the hardiest of 

 plants become sickly and succumb to the damping oft' fungus 

 when grown in a stagnant atmosphere. 



Too great a degree of soil heat and soil moisture causes 

 serious troubles, as may be seen in the case of Oedema of 

 tomatoes and the damping off" of seedlings. An excess of 

 moisture in the soil stimulates growth and often renders the 

 plant more susceptible to disease. 



An excess of water in the plant tissue is also favorable to 



