An evergreen tree retains a large portion of its green leaves all year.

scale -- A very small leaf around a dormant bud. Also other things that might remind one of fish scales on the surface of ferns, stems and the like.

fused means joined together.

A perennial plant lives and blooms for many years.

A herb is a plant whose stems die back to the ground in the winter.

ribbed -- having prominent, narrow parallel protrusions that extend over most of its length or circumference.

persistent -- When the leaves of a plant fail to fall off in the fall they are persistent. Flowers that stay around after fruiting would be persistent.

stalk -- The supporting structure of an organ. Examples of stalks are stem, peduncle, petiole, ...

spores are produced by ferns, horsetails, and other primitive plants. Spores are like tiny seeds, but they lack food for the plant embryo. Because spores are easily carried aloft by the wind, they allow ferns and horsetails to reproduce asexually across considerable distances.

sheath -- a tubular or rolled part of an organ, e.g. the lower part of the leaf in most grasses.

tubercle is generally a wart-like projection.