THE MOSS SPOROPHYTE

The sporophyte of mosses is parasitic upon the gametophytic plant throughout its life. It develops from the fertilized egg cell and remains as an outgrowth from the archegonium in the tip of the leafy plant.

Three different conditions exist as to the ease with which the sporophyte can be seen. The sporophyte stalk is always typically surrounded by perichactial leaves, and when the tips of these leaves reach above the capsule, the capsule is immersed. If these leaves reach the base of the capsule the capsule is emergent, but if the capsule is high above the leaves it is exserted. The seta may be straight or arcuate (bow-shaped).

PLATE VII. SPOROPHYTE MORPHOLOGY

PARTS OF THE MOSS SPOROPHYTE
1 - calyptra. 2 - operculum. 3 - capsule. 4 - seta. 5 - foot. 6 - peristome. 7 - annulus. 8 - urn.

TYPES OF SETA
1 - exserted. 2 - emergent. 3 - immersed. 4 - straight. 5 - arcuate.

A Sporophyte consists of a foot or absorbing base, a capsule that contains the spores, and a seta that bears the capsule aloft. The capsule is very usual in moss taxonomy. The body of it, known as the urn, bears, typically, a fringe of five teeth (the peristome) around the mouth. These teeth control the dispersal of spores from the capsule. In most mosses a circular lid, (the operculum) covers the urn and is in turn covered by a hood-like calyptra.

The capsule varies in shape, as shown in the accompanying diagrams, from globose and ovate (egg-shaped) to oblong and cylindric. A pyriform or pear-shaped capsule represents a specialized shape as does turbinate, or top-shaped. A capsule having a swelling at the base is referred to as strumose.

The position of the capsule is likewise important in identification. In forms like Orthotrichum it is commonly erect, while among the Bryums and Pohlias it is pendent or cernuous. Forms such as Ceratodon purpureus which is a common moss at many elevations in the Park, often have the capsule horizontal; i.e., at right angles to the seta, or curved.

The calyptra is usually deciduous; i.e., it falls early after development of the sporophyte, and then is not of much value in identifying the mosses. However, if it is persistent, it may be of two types. A mitrate or mitriform calyptra is ore that is split on two or more sides, while if the calyptra is hood-shaped and split on one side only, we refer to it as being cucullate.

PLATE VII. SPOROPHYTE MORPHOLOGY

TYPES OF CAPSULES AS TO SHAPE
1 - globose. 2 - ovate. 3 - oblong. 4 - cylindric. 5 - pyriform. 6 - strumose. 7 - turbinate.

TYPES OF CAPSULES AS TO POSITION
1 - erect. 2 - pendent. 3 - cernuous. 4 - curved.

TYPES OF CALYPTRA
1 - mitrate. 2 - cucullate.

The operculum in general is not of great importance in moss study. Its shape varies from a flattened convex structure to a conic or cone-shaped form. Opercula are often equipped with a short or long projection (beak). The condition in which this projection is long is referred to as long-rostrate, while the former is short-rostrate.

Peristome teeth - number, size, shape and character - are important in determining the different moss species. Some mosses do lack teeth entirely and are then known as gymnostomous. The reader will note in the section on classification in the present work that one large moss group has solid teeth (the Nematodonteae) and another jointed teeth (the Arthrodonteae).

Again, the number of teeth varies from four, as in Tetraphis (Georgia) pellucida, collected at the base of trees back of Longmire Inn, to as, many as sixty-four in the Polytrichaceae. In this family, however, the teeth are poorly developed and are difficult to discern except with a good hand lens. The usual number of teeth is sixteen.

Peristome teeth may be arranged in two rows (double peristome) in which case the inner row, known as segments, is poorly developed and thin. Mosses that have the teeth arranged in one row (single peristome) usually have sixteen teeth, although each of these teeth ma be split to the base, making thirty-two teeth.

Moss peristomes are, without doubt, among the most beautiful and interesting objects in Nature. In studying them. intact under the microscope without attempting to remove them from the capsule, I have found that a good flashlight directed upon the upturned peristome enables one to get views impossible with the ordinary lighting.

PLATE VI. SPOROPHYTE MORPHOLOGY

TYPES OF OPERCULA
1 - convex. 2 - conic. 3 - long rostrate. 4 - short rostrate.

GYMNOSTOMOUS CAPSULE

TYPES OF PERISTOMES
1 - double peristome. 2 - single peristome. 3 - peristome of Polytrichum.