[Taxacom] lectotypification?

[michele.rodda at libero.it]

Dear all, 
I am a PhD student from the University of Torino, Italy. This is my 
first message. I hope my question will be appropriate for this group. 
I have 
been dealing with the Taxonomic placement of some Hoya species whose protologue 
cites a field number, but not the herbarium where the type had been deposited.  
These names, having been published between 1906 and 1913 are valid. As the 
field number cited in the protologue is not written on one specimen only but on 
all the duplicates as well, is there the need to designate a lectotype? 

Kind 
regards, Michele Rodda