SporePlants213-page16

SporePlants213-page16 - rhizome or basal stem. Fronds

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Spore-Dispersing Vascular Plants - 16 Structural Characteristics of the Ferns Ferns are usually homosporous. The aquatic ferns are heterosporous. The vascular stem is usually an underground rhizome, or a basal stem. In tree ferns the stem is columnar, with leaves forming much of the diameter of the stem. The fern leaf is called a frond. Fronds are megaphylls, with well-developed vascular tissue. The "petiole" is called a rachis. Many fern fronds are highly dissected. Compound leaves are common. Separate sporangia-producing (fertile) and vegetative (sterile) fronds are produced in many fern species. In colder habitats, the fronds die each year, and new growth is produced from the
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rhizome or basal stem. Fronds "emerge" by circinnate vernation, a nearly unique uncoiling process. The uncoiled young fern fronds are called fiddleheads. Spores are produced in sporangia located in a sorus, which usually has a protective indusium. The indusium is a special layer of leaf tissue. The sori and their protective indusia (plural forms) vary in shape and are located on the underside of fertile fronds. Indusium location and shape is used in fern identification. Fern sori with Indusia Sori lacking an indusium...
View Full Document

Ask a homework question - tutors are online