منابع مشابه
Analysis of the physiological responses of the plane and willow trees against air pollution in Tehran .
Trees can improve air quality, but at the same time, pollution might put them at risk. Plane(Platanus orientalis L) and willow trees (Salix babylonicaL) are important trees in the green space of Tehran. Plane trees in Tehran have experienced early autumn in recent years due to severe air pollution. The present study, investigated some physiological traits of these trees under study to determine...
متن کاملThe Origin of Trees
According to Genesis, trees were created on the third day of the Creation Week. Within a Biblical worldview, this suggests that they are discontinuous with other plant forms. Naturalists posit that trees arose by random processes from simpler photosynthetic organisms. Fossil evidence for tree evolution from putative non-tree precursors is evaluated. It is concluded that the fossil record does n...
متن کاملThe butterfly decomposition of plane trees
We introduce the notion of doubly rooted plane trees and give a decomposition of these trees, called the butterfly decomposition which turns out to have many applications. From the butterfly decomposition we obtain a oneto-one correspondence between doubly rooted plane trees and free Dyck paths, which implies a simple derivation of a relation between the Catalan numbers and the central binomial...
متن کاملThe Height of Multiple Edge Plane Trees
Multi-edge trees as introduced in a recent paper of Dziemiańczuk are plane trees where multiple edges are allowed. We first show that d-ary multi-edge trees where the out-degrees are bounded by d are in bijection with classical d-ary trees. This allows us to analyse parameters such as the height. The main part of this paper is concerned with multi-edge trees counted by their number of edges. Th...
متن کاملBipartite Embeddings of Trees in the Plane
Given a tree T on n vertices and a set P of n points in the plane in general position, it is known that T can be straight line embedded in P without crossings. The problem becomes more diicult if T is rooted and we want to root it at any particular point of P. The problem in this form was posed by Perles and partially solved by Pach and Torosick 5]. A complete solution was found by Ikebe et al....
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ژورنال
عنوان ژورنال: The American Naturalist
سال: 1890
ISSN: 0003-0147,1537-5323
DOI: 10.1086/275185