The primitive cell sends colorless tubelets (rhizoids, rh.) into the mud on which it grows.
Ax., Green axis creeping on the surface of damp soil; rh., colorless rhizoids penetrating the soil; asc. ax., ascending axes of green cells.
The base of the stem bears numerous cell-filaments (rhizoids) which fix the plant to the substratum upon which it is growing.
To the base of the stem are attached a number of branched cell-threads (rhizoids) which ramify in the soil, fixing the plant and absorbing water from soil.
Where the plant lives on soil from which it absorbs its main supply of water by means of its basal rhizoids) that a water-conducting (hydrom) strand is developed.
The stem in this family falls into two divisions, an underground portion bearing rhizoids and scales, the rhizome, and a leafy aerial stem forming its direct upward continuation.
The surface layer of the rhizome bears rhizoids, and its whole structure strikingly resembles that of the typical root of a vascular plant.
In some cases the rhizoids are united together into larger strands, the rhizines.
As in the case of epiphytic brown seaweeds, the rhizoids of the epiphyte often penetrate the substance of the supporting alga.
From the first node arise rhizoids; from the second a lateral bud, which becomes the new plant.
Cernuum and other forms with superficial green prothalli is attached to the prothallus by a small foot, and develops at first as a tuberous body (the protocorm) bearing rhizoids; this forms a number of simple leaves, and upon it the apex of the shoot arises later.
A, Prothallus viewed from the lower surface; ar, archegonia; an, antheridia; rh, rhizoids (much enlarged).
The formation of a massive body naturally involves the localization of the absorptive region, and the function of absorption (which in the simpler forms is carried out by the whole of the vegetative part of the mycelium penetrating a solid or immersed in a liquid substratum) is subserved by the outgrowth of the hyphae of the surface-layer of that region into rhizoids, which, like those of the Algae living on soil, resemble the root-hairs of the higher plants.
In the liverworts we find fixation of the thallus by water-absorbing rhizoids; in certain forms with a localized region of water-absorption the development of a primitive hydrom or water-conducting system; and in others with rather a massive type of thallus the differentiation of a special assimilative and transpiring system.
These aggregations or colonies, as they are termed, may attached to muddy surfaces by rhizoids; Caulerpa, on the other, assume the form of a plate, a ring, a solid sphere, a hollow sphere, presents a remarkable instance of the way in which much the same a perforate sphere, a closed net, or a simple or branched filament.
Attached to the bottom of pools series of the Confervales, the thallus consists of filaments branched by means of rhizoids, the thallus of Characeae grows upwards by or unbranched, attached at one extremity, and growing almost means of an apical cell, giving off whorled appendages at regular wholly at the free end.
In other species of that genus an apparent cortication arises by the downward growth of rhizoids, which are retained within the gelatinous wall of the axial cells.