In this article we will discuss about the external morphology of ectocarpus.
1. Plant body consists of thin, well-branched, brown- coloured filaments arranged in heterotrichous form.
2. Heterotrichousthallus is differentiated into a prostrate system and an erect system (Fig. 36 A-D).
3. Prostrate system is creeping, septate, profusely branched and attaches the plant with the substratum, thus functioning as holdfast.
4. Each system arises from prostrate system and consists of many branched filaments.
5. Branches arise just below the septum. Branching is lateral.
6. In each branch the cells are arranged uniseriately.
7. A branch generally tapers into a series of elongated cells forming a colourless hair-like structure.
8. Each cell is rectangular and remains surrounded by a thick cell wall (Fig. 36 E, F).
9. Cell wall consists of an outer layer of pectose and an inner layer of cellulose.
10. Chromatophores are either discoid, ribbon-or band- shaped.
11. Chromatophores are irregular in outline and brown in colour.
12. Pyrenoid-like naked bodies are also sometimes seen in the cell.
13. The cells are uninucleate having mannitol and laminarin as reserve food.