Cell-wall studies in the Chlorophyceae. I. A general survey of submicroscopic structure in filamentous species

Abstract

The paper constitutes a survey of the fine structure of the walls in about sixty species of filamentous green algae, as revealed chiefly by the methods of X -ray analysis. With some species use has also been made of the polarizing microscope and of staining reactions. I t is known that wall constituents in the algae are very variable, and one aim of the investigation has been to systematize this variation. The chief aim has been, however, to attempt to delimit the range of types which show the ‘crossed fibrillar’ structure typical of Valonia . It has been found possible, on the basis of wall characters, to divide the algae investigated into three rather ill-defined groups, as follows: Group 1. The algae of this group contain native cellulose (cellulose I) as a major skeletal substance. The cellulose is highly crystalline and shows the ‘crossed fibrillar’ organization. Members of this group are found only in the Cladophorales, and in a few members of the Siphonales. Group 2. The skeletal substance of the walls in this group possess intermolecular spacings which approximate to those of mercerized cellulose (cellulose II). There is some evidence that, in some cases at least, the substance is not mercerized cellulose but some cellulose derivative. It is poorly crystalline and normally in random orientation. The large bulk of the algae fall into this group, which includes the Spongomorpha section of Cladophora . Group 3. This is a small, heterogeneous collection of algae in which the skeletal substance either is not cellulose in any known form, or shows abnormalities, in what otherwise might be an X-ray diagram of cellulose, which make identification difficult. Prominent among the latter may be mentioned Spirogyra and Vaucheria . It is suggested that wall studies of this kind would repay consideration by taxonomists, particularly as regards the status of the Cladophorales,