Some Observations on the Spikelet of Hierochloe odorata

Abstract

During the summer of 1958 the writer spent several weeks in Iceland durilig which time specimens of Sweetgrass, Hierochloe odorata (L.) Beauv., were collected in several localities. A visit to Sluttnes, a very small island in Lake Myvatn in northern Iceland, resulted in the collection of four rather robust looking specimens of this interesting grass. These uponi later examination proved to be abnormal with respect to certain structures of the spikelet. Observations.-It was found that two of the four specimens from Sliuttnes possessed spikelets having four florets each; the third plant was intermediate having spikelets with four florets only in the upper part of the infloreseence, while the fourth specimen had normal spikelets of three florets. In normal spikelets of Hierochloe' the first two florets are male and each has three stamens; the terminal third floret is perfect and has just two stamens. In the abnormal plants from Sluittnes the first two male florets also have three stamens each, but the perfect third floret has three stamens rather than two and, in addition, there is a perfect fourth floret with two stamens. These characteristics are illustrated in figure 1. The Sluttiies plants thus are different in two ways: the spikelets have a perfect fourth floret of reduced size, and the third floret has three stamenls instead of the usual two. Dr. Thorv. Sorensen (personal communication) of the Universitetets Botaniske Laboratorium, Copenhagen, considerately examined 44 specimens of Icelandic Hierochloe' odorata in the collections of that institution and found that a plant collected by Grontved on Sl?uttnes in 1935 was of the kind having four florets per spikelet. The only other anomalous specimen Sorensen found was one from Mbdruvallanes which had spikelets made up of one staminate and two perfect florets. It should be mentioned here that the writer has found no deviations in floret number in his specimens of Hierochloe' odorata collected in other parts of Iceland nor has he observed such anomalies in any of his colleetions of this grass made in the United States. The plants collected on Sl?uttnes probably come from a well established clone in which culms bear-