The Role of Leaves and Roots in the Control of Inflorescence Development in Carex

By using aseptic culture methods it has proved possible to studythe roles of leaves and roots in the control of inflorescenceinitiation and development in Carex. Removal of leaves upsetsinitiation and growth of the inflorescence and it is concludedthat the continued stimuli from the leaves essential for normaldevelopment are not supplied by leaves appreciably less thanhalf grown. Removal of roots or root apices upsets inflorescenceinitiation and branching. It is probable that a stimulus fromthe roots promotes initiation but is not essential, whereasa factor produced by actively growing roots is essential fornormal branching to occur. The only substance tested which couldalter the degree of branching was benzyladenine. On the evidenceavailable it is suggested that normal branching of the inflorescencemay depend on an adequate supply of cytokinin from the roots.     

Vetulicolians from the Lower Cambrian Sirius Passet Lagerstätte,North Greenland,and the polarity of morphological characters in basal deuterostomes

Abstract: Vetulicolians are problematic Cambrian fossils with a debated phylogenetic history. Here, we describe two vetulicolian specimens from the Lower Cambrian Sirius Passet locality in North Greenland. One of the specimens is assigned to Ooedigera peeli gen. et sp. nov, whereas the other is retained under open nomenclature. The mode of tail flexibility has been debated in the literature, and we argue here that the tail normally flexed laterally to generate power strokes rather than dorsoventrally. The phylogenetic relationships of vetulicolians are discussed in the light of current knowledge of deuterostome phylogeny and morphology, and it is concluded that the best hypothesis on currently available evidence is that vetulicolians are a clade or paraphyletic assemblage of stem‐Deuterostomata. The presence of a voluminous, sediment‐filled anterior chamber suggests that the atrium may be a synapomorphy of deuterostomes.