Doubt in Combline Filter

Hello All

Here is a line from a paper by Matthaei [1] that I was not able to understand. He says

If the resonators in a combline filter is full λ0/4 long at resonance and the structure would have no pass-band. Without some kind of reactive loading at the ends of the resonator line elements, the magnetic and electric coupling effects would cancel each other, and the comb-line structure would become an all-stop structure.

I read another paper coauthored by him that talked about the same topic but I couldn't make anything out of it.

Can some one clarify

Ref:
1. G.L.Matthaei, "Comb-line Band-pass Filters of Narrow or Moderate Bandwidth", The Microwave journal, pp 82-91 (Aug 1963)
2. Bolljahn,J.T and G.L.Matthaei, "A study of the phase and filter properties of arrays of parallel conductors between ground planes", Proc. IRE 50, pp 299-311 (march 1962)

Thanks