1921] EMERSON—BOG PLANTS 373 
that induces shallowness. Doubtless the lack of oxygen plays a con- 
siderable part in checking growth under water. It is possible that 
bog toxins may in part be responsible for the poor development or 
in some cases even the death of the roots of certain species. 
Summary 
1. Subterranean systems of plants growing on floating mats 
were found to be very superficial, nearly all the living tissue being 
above the level of the water. 
2. No evidence was found to suggest that acidity or toxins are 
involved in the shallowness of these organs. Water level was 
apparently the important factor, aside from hereditary tendencies 
in certain species. 
3. Roots of codominants were in close — without 
apparent damage resulting to them. 
4. Three types of behavior were noted, sasha in the super- 
ficial placing of the living parts of bog plants: (a) the parts assume 
the horizontal position above the water level; (6) the tap root is 
ephemeral in the bog and is replaced by horizontal laterals; (c) the 
roots are all vertical and die at the water surface. 
5. Certain plant parts ' were found to be able to thrive under the 
water in the bogs. 
6. There is no apparent marked difference in the subterranean 
organs of a given species growing in a bog and in comparable con- 
ditions in mineral soils. 
I wish to express my appreciation to Dr. H. C. CowLes and 
Dr. Geo. D. Futter for encouragement and helpful suggestions 
during the progress of this work. 
PENN COLLEGE 
Osxatoosa, Iowa 
LITERATURE CITED 
1. CANNON, W.A., The root habits of desert plants. Carn, Inst. Wash. Publ. 
Tar. 20tt. 
. , Notes on root variation in some desert plants. Plant World 16: 
323-341. I9T3. 
3. Haypen, Apa, The ecological subterranean anatomy of some plants of a 
prairie province in central Iowa. Jour. Bot. 6:87-105. r1919. 
