CULTIVATION OF MEDICINAL PLANTS. 731 



penetrated by the moisture; or if the seeds are large, they may 

 be filed in one or two places ; when they are small they may be 

 shaken with sharp, angular sand until the exterior is somewhat 

 roughened. 



After the seedlings have put forth a few leaves they are then 

 set out in suitable boxes known as flats (Fig. 401) which contain 

 a soil having a fair amount of nutriment. The plants must be 

 watched at this point to see that there is no damping off and loss 

 by reason of attacks by soil micro-organisms. 



Fig. 402. Cold frames for use in propagating such plants as Digitalis, Belladonna, 

 Henbane, etc. The young seedling plants are transferred from the greenhouse to these 

 cold frames in late spring for th^ purpose of hardening them before transplanting to the 

 open field. — From the Experimental Farm of Eli Lilly & Company, Indianapolis, Ind. 



Should there be a damping off and loss of seedlings some 

 method should be employed to overcome it. Recently the De- 

 partment of Agriculture has utilized dilute sulphuric acid, which 

 Kraemer has shown is the active principle produced whenever 

 sulphur is used in the greenhouse, for the destruction of insect 

 pests, as well as the blights due to fungi and other micro- 

 organisms. 



The plants are allowed to grow in the flats until they have 

 developed a good root system and have produced a shoot with 

 3 or 4 leaves. They are then transferred to cold frames (Fig. 

 402), where they remain until they are acclimatized or hardened 



