Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: A CONTRIBUTION TO THE LIFE HISTORY OF SILPHIUM. CONTRIBUTION FROM THE HULL BOTANICAL LABORATORY. XVII. William Dayton Merrell. (with Plates 1n-x) INTRODUCTION. The flowers of Compositae are favorable for morphological study, in that several closely connected stages may be obtained in a single section. The broad outlines of the organogeny of the flower were early discovered, and it has only remained for later investigators to examine the more minute details. Aside from an interest in the family as being the highest among dicotyledons, the division of labor among the flowers of a head deserves attention. This is carried so far in Silphium that the ray-flowers are ovulate and without stamens; while the disk-flowers are staminate and without ovules, the style never forking. It might be expected that some transitional stages in the abortion of stamens or of ovules could be found, and the present study was undertaken with that in view. The results obtained in this particular were very meager, but the investigation led to the discovery of several unexpected phenomena, which are herewith presented. MATERIAL AND METHODS. The material was collected during the summers of 1896, 1897, and 1898, in the vicinity of Chicago. Unfortunately, most of the collections had to be made in the latter part of the day, and this probably accounts for the small number of cells found in process of division. Even in the youngest buds it was found to be advantageous to pick off the outer involucral scales, partly 1900! 99 because they interfered with the rapid penetration of the fixing fluid, but more especially because their brittleness very quickly spoiled the edge of the microtome knife. The older akenes, containing embryo-sacs or embryos, were picked off separately, and cut one at …
