Weights of Seeds and Numbers Per Plant

were air dried for two weeks or more, threshed and cleaned to remove immature seeds, empty florets, etc. In some cases (Epilobium, Pyrola), visual examination had to replace the usual cleaning. This method serves well for species the seeds of which are retained until all are mature. For species in which ripening extends over a considerable period and seeds are shed as soon as mature, only a part of the total number can be secured at a single collection. In most cases that number is given, with footnotes to indicate that more would have developed, or if some had already dropped. As noted in the previous report (3) the total yield for these plants might be estimated at twice as many if some had dropped or had not matured or four times as many if both factors prevailed. In a few cases daily collections were made or (Lactuca scariola, L. biennis) heads were counted and total number estimated. In some plants seeds were extensively damaged by insects and this is noted. In most cases the total number listed is that of good seeds only for one plant. In those groups where seed is not separated readily from fruit the weights are usually of the fruit or parts thereof, such as caryopsis with lemma and palea, achenes, nutlets or mericarps. For perennials which increase in area, a single stalk was usually taken. The propriety of choosing an plant has been discussed by Salisbury (2) who sought to obtain average yields from a large number of individuals. However, conditions vary so widely that averages would be valid only for the conditions under which samples were taken. Production by occasional plants that survive in fields is an important item which is often overlooked. Further discussion is made under a few species. Material is from North Dakota unless otherwise indicated. A few species have been duplicated, usually without intention. Specimens from the same lot of a few species have been distributed to several