CONTENTS

CHAP.PAGE
I.[Introduction][1]
II.[Methods of Working][7]
I.[Discussion of Methods][7]
1.[Water cultures][7]
2.[Sand cultures][8]
3.[Soil cultures in pots][9]
4.[Field experiments][9]
II.[Details of Methods][10]
III.[Effect of Copper Compounds][15]
I.[Presence of Copper in Plants][15]
II.[Effect of Copper on the Growth of Higher Plants][17]
1.[Toxic effect][17]
(a)[Toxic action of copper compounds alone in water cultures][17]
(b)[Masking effect caused by addition of soluble substances to solutions of copper salts][20]
(c)[Effect of adding insoluble substances to solutions of copper salts][22]
(d)[Effect of copper on plant growth when present in soils][24]
(e)[Mode of action of copper on plants][25]
2.[Effect of copper on germination][27]
(a)[Seeds][27]
(b)[Spores and pollen grains][28]
3.[Does copper stimulate higher plants?][28]
4.[Action of copper on organs other than roots][30]
(a)[Effect of copper sprays on leaves][30]
(b)[Effect of solutions of copper salts on leaves][32]
III.[Effect of Copper on Certain of the Lower Plants][33]
[Conclusion][35]
IV.[Effect of Zinc Compounds][36]
I.[Presence of Zinc in Plants][36]
II.[Effect of Zinc on the Growth of Higher Plants][38]
1.[Toxic effect][38]
(a)[Toxic action of zinc salts alone in water cultures][38]
(b)[Effect of soluble zinc salts in the presence of nutrients][39]
(c)[Effect of zinc compounds on plant growth when they are present in soils][41]
(d)[Mode of action of zinc on plants][43]
2.[Effect of zinc compounds on germination][43]
3.[Stimulation induced by zinc compounds][45]
(a)[Stimulation in water cultures][45]
(b)[Stimulation in sand cultures][46]
(c)[Increased growth in soil][46]
4.[Direct action of zinc salts on leaves][47]
III.[Effect of Zinc on Certain of the Lower Plants][48]
[Conclusion][50]
V.[Effect of Arsenic Compounds][51]
I.[Presence of Arsenic in Plants][51]
II.[Effect of Arsenic on the Growth of Higher Plants][52]
1.[Toxic effect][52]
(a)[Toxic action of arsenic compounds in water cultures in the presence of nutrients][52]
(b)[Toxic effect of arsenic compounds in sand cultures][57]
(c)[Toxic effect of arsenic when applied to soil cultures][57]
(d)[Physiological considerations][59]
2.[Effect of arsenic compounds on germination][60]
3.[Do arsenic compounds stimulate higher plants?][61]
III.[Effect of Arsenic Compounds on Certain of the Lower Plants][62]
1.[Algae][62]
2.[Fungi][63]
[Conclusion][64]
VI.[Effect of Boron Compounds][65]
I.[Presence of Boron in Plants][65]
II.[Effect of Boron on the Growth of Higher Plants][67]
1.[Toxic effect][67]
(a)[Toxic action of boron compounds in water cultures][67]
(b)[Toxic action of boron compounds in sand cultures][70]
(c)[Toxic action of boron compounds in soil experiments][71]
2.[Effect of boron compounds on germination][72]
3.[Does boron stimulate higher plants?][73]
(a)[Water cultures][73]
(b)[Sand cultures][73]
(c)[Soil cultures][74]
III.[Effect of Boron Compounds on Certain of the Lower Plants][76]
[Conclusion][77]
VII.[Effect of Manganese Compounds][78]
I.[Presence of Manganese in Plants][78]
II.[Effect of Manganese on the Growth of Higher Plants][81]
1.[Toxic effect][81]
(a)[Toxic action of manganese compounds in the presence of soluble nutrients][81]
(b)[Toxic action of manganese compounds in sand cultures][82]
(c)[Toxic action of manganese compounds in soil cultures][82]
2.[Effect of manganese compounds on germination][84]
3.[Does manganese stimulate higher plants?][84]
(a)[Stimulation in water cultures][85]
(b)[Stimulation in soil cultures][86]
III.[Effect of Manganese Compounds on Certain of the Lower Plants][90]
IV.[Physiological Considerations of Manganese Stimulation][90]
[Conclusion][92]
VIII.[Conclusions][93]
[Bibliography][97]
[Index of Plant-Names][107]
[General Index][109]
[List of Illustrations][x]