It is the species & old-fashioned hybrids, which interest us.  Their flowers, their foliage & their structure all bear no relation to the modern aberrations which fill garden centres.  Among old-fashioned Pelargoniums the diversity of flower, leaf shape, leaf scent & plant structure is truly amazing.  Many of them will grow into large shrubs - P. Purple Unique reaches 300cm. Others have enormous leaves - P. tomentosum has mature leaves 30cm. across.  Some have leaves, which are the merest filigree - P. abrotanifolium. Some have the daintiest of flowers - P. fragrans, a haze of tiny white flowers.  Others have flowers with the richest of hues - P. Lord Bute, intense purple black flowers edged with red.  Some are scented of lemon, others of pine or balsam or peppermint.