The Proceedings of the Iowa Academy of Science Volume 20 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ...to "the point where the common deciduous trees are affected. At times there may be noticeable effects, but from a practical point of view conditions are not looked upon as being serious even if conifers are not able to thrive. Belt (7) represents a step in advance of the former in that it permits conifers such as the pines, to have a normal development. Since the Des Moines survey another belt in advance of the previous one has been marked out. This zone is conveniently designated as the Pleurococcus belt. The idea of using Pleurococciis as a possible index to smoke injury was brought to my attention by Dr. William Crocker of the University of Chicago. He noted that trees in the vicinity of the University and in Jackson and Washington Parks did not have any Pleurococcus upon their trunks. Even trees possessing a sufficient amount of shade and having more than sufficient moisture were without the green material upon the north side. The territory studied at Chicago did not offer conditions which would permit of a mapping out of a Pleurococcus 'belt. That it too is an index for a small amount of smoke injury was noted in the Des Moines survey. On account of great amount of rainfall in the fail this was readily done. For instance, when the residence portion of Des Moines on the west side begins at 12th St. the pines or the 6th zone will be marked out from 18th St. to 32d St. At this point Pleurococcus is noted for the first time. Similar conditions are noted on the east, north and south sides of the city. It may be well to point that the Lichens are even more susceptible to smokes and gases than Pleurococcus. The result? of the restricted survey show: that smoke and gases present in industrial cities have a detrimental effect upon the vegetation in...