SUBPHYLUM SPHENOPHYTA or HORSETAILS

• includes only about 20 living species of plants
• ancient forms were as big as trees
• modern forms are usually less than a meter high
• common in shaded woods and around stems, swamps and ponds
• sporophytes have true roots and leaves, stems are green and hollow
• cone-shaped spore producing structures form at the ends of some stems
• haploid spores give rise to small gametophytes by meiosis and bear reproductive organs
• zygote gives rise to a sporophyte after fertilization
• stems contain crystals of silicon
• used for scouring pots and pans by early settlers which made them known as the scouring rushes

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