Question: Why are green algae not classified as plants? Need Assignment Help? Multiple Choice Plants enclose and protect the embryo within the female plant, while green algae do not. Green algae have a cell wall of chitin, while plants have cell walls of cellulose. Algae are sporophytes that reproduce only asexually, while plants are gametophytes and reproduce sexually. All plants are vascular, while all green algae are nonvascular. The green algae use chlorophyll a, while plants use chlorophyll b.