HENDERSON'S HANDBOOK OF PLANTS. 



BUS 



ened condition of the plant that invites 

 the attacks of parasites, causing the 

 "rust." This we have proved to be the 

 case so often in our practice, that we 

 now no longer doubt on the subject. 



We find, for example, if we leave such 

 plants as Heliotrope, Verbenas, Lanta- 

 nas, Pelargoniums, or other plants subject 

 to the disease known as "black rust," so 

 that they become enfeebled for want of 

 pot room, they are almost certain to be 

 affected. A few years ago we tried an 

 experiment on one hundred each of He- 

 liotrope and Verbena plants, (that were 

 in fine healthy condition, growing in two- 

 inch pots,) of shifting one-half of each lot 

 into three-inch pots, the other half being 

 allowed to remain unshifted. The shift- 

 ed plants grew vigorously, and in six 

 weeks were twice the size of the others, 

 and in fine, vigorous health; while those 

 unshifted, becoming impoverished for 

 want of new soil, were stunted, and near- 

 ly all became affected by "black rust." 



The examination of the diseased leaves 

 by a powerful microscope revealed num- 

 bers of crab-like mites feeding on the 

 leaves, while on healthy leaves of the 

 same plant not a parasite could be found. 

 The inference then is, that the weak- 



SCA 



ened condition of the plant made it a 

 congenial soil for the deposit of the germ 

 of this parasitical insect. Another kind 

 of "rust," evidently distinct from the 

 preceding, is now one of the most serious 

 obstacles to the forcing of Lettuce under 

 glass, whole crops being utterly destroy- 

 ed by it. We are inclined to believe that 

 the Lettuce rust is the work of a vegeta- 

 ble parasite, as a microscopic examina- 

 tion of the diseased leaves show a fungoid 

 structure very similar to Eose mildew. 

 The only remedy we can advise in this 

 case is to work with young plants on fresh 

 soil, as far as practicable. The usual 

 method of obtaining Lettuce plants for 

 forcing, is to use plants sown or planted 

 in cold frames in fall, for all the plantings 

 during the entire winter; but we have 

 found that such plants are more liable to 

 the disease than those sown later; and 

 now the most successful growers of Let- 

 tuce for winter, use only the cold frame 

 (fall sowed plants) for their first crop, 

 which is usually ready at Christmas, 

 while for the succession crops, new sow- 

 ings are made about six weeks before the 

 plants are needed, it being found that 

 these fresh young plants are less liable to 

 the rust than the others. 



s. 



, Sabulosus. Growing in sandy 

 places. 



Saccharate. Having a sweet taste. 

 Sacciform. Having the form of a bag. 

 Sagittate. Shaped like an arrow. 

 Samara. An indehiscent fruit producing a 

 wing-like expansion from its back or end. 

 Sap. The juice of a plant. 



Sapid. Having an agreeable taste. 

 Sapor. The taste which a thing has. 

 Sarmentum. A runner. 

 Sarmentose. Producing runners. 

 Sujcatttis. Growing on rocks or stones. 

 Scabrous. Hough with little asperities. 

 Scales. Minute rudimentary leaves. 

 Scandens. Climbing, but not twisting. 



