IUNAVAILABILITY OF IRON AS A CAUSE OF FRENCHING OF TOBACCO (NICOTIANA TABACUM L.)'1 Y FIGURES)
In continuation of the work reported by JONES (4) the effort has been directed toward investigating the factors in the soil which induce frenching of tobacco (Nicotiana Tabacum L.) at a soil temperature of 350 C. and which are impotent at a soil temperature of 21° C. Previous work (4), while not discounting the soil toxin theory, did suggest that biological activity of soil flora might alter the availability of a nutrient element and thereby upset a physico-chemical balance which might disturb normal development of the plant. Since it is recognized that a soil flora is a complicated society affected by environment, particularly moisture and temperature, no attempt has yet been made to sort out the various organisms to ascertain which, if any, might be responsible for depriving a plant of its requirements. During the process of the investigation certain experiments were performed and special studies made, which, although the results had no bearing on the final conclusions, are reported in this paper as contributions pertinent to information on the subject of frenching.
FRENCHING OF RAGWEED ( AMBROSIA ARTE , lIISIIFOLIA L . )
Typical frenching of tobacco (Nicotiana tabacum L.), as described by WOLF (8), is recognized as producing short internodes, loss of apical dominance, and the development of a rosette of many leaves (polyphylly), giving a witches'-broom effect. The first symptoms appear as a pinhead chlorosis, followed by very chlorotic, newly developing leaves which narrowly elongate with wavy margins. It is possible that the tobacco plant (Nicotiana tabacum L.) is the best indicator plant to determine the presence of the frenching factor in the soil. This peculiar develop'ment of the leaves of tobacco has never been found to be associated with a pathogenic bacterium, a fungus or a virus. It is generally recognized as a nonparasitic disease and therefore considered physiological. STEINBERG (5, 6) has worked with many tobacco soil organisms which are not considered pathogenic but which miglht produce a diffusate sufficiently toxic to produce the symptoms of frenching. One of these, Bacilluts cereus Frankland and Frankland, was found to be capable of producing the frenching symptoms. STEINBERG (7) has found this organism to be present in greater numbers in the rhizosphere of tobacco in soils that. contained frenched tobacco than in the soils with normal plants. The origin of this disease is some soil factor. The frenching factor is not in all soils but has been found, in particular, in soils which are known to remain moist during a prolonged drought period, even though tobacco has never been grown in such soils. Continuing the work previously reported (2, 3), it has been demonstrated that the frenching factor, if present, can be made to show its presence by growing tobacco plants at a soil temperature of 350 C. Usually within a period of 5 to 15 days frenching symptoms appear in the newly developing leaves, becoming more distinct and severe with succeeding leaves. When the soil temperature is 210 C, or less, the presence of the frenching factor does not become evident. During the investigation of the relationship of soil temperature to the frenching factor that affects tobacco, many volunteer weed plants of various genera appeared in the soils employed in the study. Ragweed (Ambrosia arteinisiifolia L.), as a w*eed, frequently showed chlorotic symptoms on leaves that were so narrow they appeared like starched string. These symp-
American Insurgents, American Patriots: The Revolution of the People
This is a story of rumour, charity, vengeance, and restraint. "American Insurgents, American Patriots" reminds us that revolutions are violent events. They provoke passion and rage, a willingness to use violence to achieve political ends, a deep sense of betrayal, and a strong religious conviction that God expects an oppressed people to defend their rights. The American Revolution was no exception. A few celebrated figures in the Continental Congress do not make for a revolution. It requires tens of thousands of ordinary men and women willing to sacrifice, kill, and be killed. Breen not only tells the history of these ordinary Americans but, drawing upon a wealth of rarely seen documents, restores their primacy to America's road to independence. Mobilizing two years before the Declaration of Independence, American insurgents in all thirteen colonies concluded that resistance to British oppression required organized violence against the state. They channeled popular rage through elected committees of safety and observation, which before 1776 were the heart of American resistance. "American Insurgents, American Patriots" is the stunning account of their insurgency, without which there would have been no independent republic as we know it.