SUBROUTINE  VISTS (Z1,ZE,Z2,N,M)

C     [TRIANGULAR SEQUENCE]
C     ZE(M,M)  ARRAY OF VALUES
C     Z1,Z2    RANGE OF VALUES
C     N        ACTUAL  LENGTH OF COLUMN
C     M        MAXIMUM LENGTH OF COLUMN
C     [05-OCT-74]

      EXTERNAL    PLTCA
      DIMENSION   ZE(1),U(501),V(501)

      IX(J,I)=(I-1)*M+J
      AM(J,I)=ZS*(ZE(IX(J,I))-Z1)

      MK=501
      HZ=0.35
      ZS=(2.0*HZ)/(Z2-Z1)
      DU=1.0/FLOAT(N-1)
      DV=0.3/FLOAT(N-1)
      HU=0.5*DU
      VE=0.0
      L=N-1
      DO 30 I=1,L
      K=0
      EU=HU*FLOAT(I-1)
      DO 10 J=I,N
      K=MIN0(K+1,MK)
      U(K)=EU
      V(K)=VE+AM(J,I)
   10 EU=EU+DU
      CALL VISHO (U,V,K,1,PLTCA)
      K=0
      EU=HU*FLOAT(I-1)
      DO 20 J=I,L
      K=MIN0(K+1,MK)
      U(K)=EU
      V(K)=VE+AM(J,I)
      K=MIN0(K+1,MK)
      U(K)=EU+HU
      V(K)=VE+DV+AM(J+1,I+1)
   20 EU=EU+DU
      K=MIN0(K+1,MK)
      U(K)=EU
      V(K)=VE+AM(N,I)
      CALL VISHO (U,V,K,-1,PLTCA)
   30 VE=VE+DV
      RETURN

      END