calculations, which attempted to discuss the problem as a unidimensional one. Dr. D. R. Inglis directed attention to Prof. Urey's view that the lighter constituents of the earth might have condensed first. Thus heavier materials trapped in the outer parts of the earth might drop down through the core from time to time. This might provide an explanation of the variations of the length of the day and would also provide an alternative explanation of the cause of core motions.
When Pax (1) in 1889 constituted his section Sinenses, he was well aware that it contained at least three distinct groups, each of which could with good reason be regarded as separate sections. Of these the one which he designated Poculiformia is the equivalent of Obconica. This group Poculiformia (while sharing in the general definition of Sinenses) he marked off by the beaker-shaped calyx which is generally accrescent after anthesis. In his view the group comes nearer to group Cortusina (i.e. section Cortusoides) than to the more isolated Auganthus (i.e. Sinenses sensu restricto), which may quite well be the case. In its turn the group Cortusina is to be distinguished from Poculiformia by the character of its calyx—a tubular or cylindrical structure. Of the species quoted by Pax as within Poculiformia, only four are now considered legitimate members of Obconica—P. obconica, P. filipes, P. Listen, and P. oreodoxa.
The typical species of this small section and the first to be described is P. cuneifolia. Within its compass are three other plants which in their time have been given specific diagnoses but are here regarded as coming more properly into the category of subspecies—P. saxifragifolia, P. hakusanensis, and P. heterodonta. P. cuneifolia, thus interpreted, has a distribution extending from N.E. Siberia to Japan, the Aleutian Islands, and the Alaskan coast. The section contains two other species—P. nipponica which is confined to Japan, and P. suffrutescens from the Sierra Nevada of California, thus widely separated geographically.
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