On the Failure of the Red Clover. 331 



much as will poison the soil upon which it grows for ten or twelve 

 years, how is the same plant enabled to live continually in the 

 midst of its own accumulated excretions ? In fine, the conclusions 

 of Macaire's experiments have been disproved by Meyen and 

 Unger. They obtained excretions from those plants only whose 

 roots had been mutilated by their removal from the soil into 

 water, which is not their natural medium of growth; but in 

 employing water-plants, and placing them in various solutions, 

 they could not detect by the most delicate re-agents the rejection 

 of any of the absorbed agents. ( See ' Root,' Penny Cyclo- 

 paedia.) 



But the following anatomical and pathological examination of 

 the dying red-clover plant will prove that no poison received by 

 the roots is concerned in its death ; for plants which are poisoned 

 assume a very different appearance. 



During the last winter I took from different fields, and particu- 

 larly from the clover-sick portion of the before-named field, a 

 great number of dying plants at different periods of the winter, 

 and examined them with the microscope, slices of whose stems 

 and leaves were placed under a magnifying power of 100 to 150 

 diameters. The part first injured is the neck of the plant (collet), 

 about a quarter of an inch below the point where the leaves join 

 the stem. If slices of the neck be placed under the microscope 

 in the early stage of the injury, the sap-vessels are found simply 

 ruptured; while, if the plant has been some time affected, as 

 shown by its foliage, a dark spot will be seen in the centre of the 

 stem, and the more external parts of a brown colour ; and, as 

 the disease spreads upwards, the stem becomes black in its entire 

 thickness, decomposition takes place, and the plant rots away a 

 little below the base of the leaves. This destruction of the 

 cellular tissue is owing to the severity of the frost; and if the 

 common cauliflower or the celery-plant at the same period of 

 the year be examined, the same effects are visible. In the cauli- 

 flower, about 3 inches below the leaves, the centre of the stalk is 

 found in its early stage simply softened, afterwards it assumes a 

 brown colour, and emits, if broken, a putrid smell, decomposition 

 having taken place. In the celery-plant, the neck becomes filled 

 with a brown sap, and the blanched leaves soon take on the ap- 

 pearance of frost-bitten celery. The first external symptom of 

 the disease in all the plants is a spotted-yellow and dead appear- 

 ance of the edges of the leaves, which takes place first in those 

 most developed, while the leaves recently expanding seem healthy, 

 but subsequently the whole plant above the neck becomes of a 

 dark colour, and if pulled breaks off, leaving the lower portion of 

 the roots healthy in appearance. 



There is no doubt that the disease is immediately caused by 



z2 



