Pinguicula is a herbaceous perennial. The plant consists of a flattened rosette of prostrate leaves and a fibrous root system. Each species has a characteristic leaf shape which is a variation of a basic elongated oval terminating in a blunt point. The edges of the leaves exhibit varying degrees of rolling in and are green to yellow-green to reddish in color. (Fig. 5-1) Most Pinguicula are homophyllous, meaning the leaves have the same shape and size throughout the entire growing season. The heterophyllous Pinguicula produce leaves after flowering that differ from leaves produced before flowering in size and shape. These are listed in Chart 1. Tentacles and sessile glands cover the leaf surfaces.
Flowers are borne singly on scapes in the spring, with some of the tropical species
Fig. 5-1 Pinguicula plant.
flowering a second time later in the growing season. Plants, depending on the species, may have one or more flower scapes which are usually covered with tentacles.
Flower color ranges from shades of yellow, white, blue, and violet to purple. The zygomorphic flowers are sympetalous with the bottom 3 petals forming the lower lip of the flower and the top 2 petals forming the upper lip. The closed, cylindrical end of the corolla narrows to almost a point forming the spur. On the lower lip of the floor of the entrance to the flower is a raised, pubescent structure called the palate, whose degree of exsertion depends upon the species. (Photo 5-1) The flower has 2 curved stamens lying flat on the corolla with the 2 anthers almost touching each other and covered by part of the pistil. (Fig. 5-2)
The fungal odor of Pinguicula is believed to be a prey attractant. Insects are trapped when they light or crawl on the surface of the leaves which are coated with a sticky mucilage. Only the smallest insects can be captured. Usually the struggling of insects attempting to escape results in their being hopelessly entrapped, as well as being suffocated, by the mucilage. The prey is digested and the digestion products absorbed for use by the plant. Pinguicula leaves show little motion during prey capture, as compared to the Sundews. What little motion occurs does not aid in prey capture. The margins of the Pinguicula leaves tend to curl up during and after prey capture to form a shallow bowl which contains the digestive fluids and prevents loss of prey. (Photo 5-2) Often the leaves tend to become distended beneath the spot where larger insects have been trapped.
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