Variation in Mentha arvensis L. (Labiatae). I. The North American populations

Most North American populations of Mentha arvensis differ from those in Europe in leaf and calyx characters, but the extremes of variation overlap. However the former have a diploid chromosome number of 96 and the latter 72. The North American populations are morphologically very variable and much of this variation is genotypic. However, none of it is discrete and, as it shows little geographic or ecological coherence, taxonomic recognition appears undesirable.
The following chemical races based on essential oil composition, occur in North America:
Type 1–high in pulegone, isomenthone and menthone.
Type 2–high in linalool, cfr-ocimene and trans-ocimene.
Type 3–high in cw-isopulegone and fnmi-isopulegone.
Type 4–high in cis- and trans-ocimene and in 1,8-cineol.
These four chemotypes are not correlated with any of the morphological variations. The recognition of chemical races is discussed and it is concluded that where possible they should be based on diagnostic components, rather than on quantitative differences or the mere presence or absence of given compounds. The literature relating to biosynthesis and essential oil composition in Mentha arvensis is reviewed.     

Structure and Operation of the Feeding Apparatus in a Colorless Euglenoid,Entosiphon sulcatum1

Entosiphon sulcatum is a phagotrophic euglenoid. The tubular ingestion apparatus, called a siphon, is composed of three microtubular rods extending the length of the cell. Within the tube are four large striated vanes arranged much like the blades in a pinwheel. The vanes arise from the microtubular rods and curve towards the center of the feeding apparatus. Sheets of endoplasmic reticulum are positioned adjacent to each of the vanes and surround the perimeter of the apparatus. A cap, supported by a scaffold and anchored into the cytoplasm, covers the opening of the siphon. An elongate invagination of the plasma membrane is positioned adjacent to the edge of the cap and extends downward into the siphon forming the opening. The vanes converge at the anterior end of the siphon and surround the invagination. During feeding, the siphon protrudes from the cell. As the apparatus protrudes the cap is withdrawn to the side, opening the siphon. The vanes spread apart expanding the invagination of the plasma membrane into a large cavity into which ingested food particles are taken.