 Experts disagree about the number of species in the genus <unk> ( broadly defined ) . In 1965 , Dutch <unk> Jan Gerard <unk> Boer estimated that there may be as many as 100 species in the genus . In their 1996 Field Guide to the <unk> of the Americas Andrew Henderson and <unk> recognised 29 species in the genus , while Sidney <unk> recognised 65 species in his 1999 treatment of the group . Largely following <unk> 's lead , <unk> <unk> and John <unk> recognised 67 species in their 2005 World <unk> of <unk> . An important element of this disagreement is the decision by <unk> to define species more narrowly than Henderson . As a result , what Henderson interpreted as variation within species , <unk> took as differences between <unk> similar species . This problem is complicated by the fact that many of these species are poorly represented in <unk> collections . The large size of the leaves , inflorescences and fruit of many <unk> species makes them difficult to collect . In addition , many important collections , including type specimen , have been lost or destroyed . <unk> or incomplete collections make it difficult to differentiate variation within a single species from variation between different species . 
