The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8
COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
3M Company COM 88579y101 18,440 112,167 SH   SOLE   0 0 112,167
A T & T Inc New COM 00206r102 334 8,838 SH   SOLE   0 0 8,838
Abbott Labs COM 002824100 1,250 14,939 SH   SOLE   0 0 14,939
Abbvie Inc. Com COM 00287y109 1,175 15,520 SH   SOLE   0 0 15,520
Alcon Inc COM H01301128 5,260 90,232 SH   SOLE   0 0 90,232
Alphabet Inc Cap Sk Cl A COM 02079k305 858 703 SH   SOLE   0 0 703
Amazon.Com Inc COM 023135106 2,715 1,564 SH   SOLE   0 0 1,564
Apple Computer COM 037833100 14,314 63,911 SH   SOLE   0 0 63,911
Auto Data Processing COM 053015103 33,421 207,044 SH   SOLE   0 0 207,044
BP PLC ADR COM 055622104 201 5,300 SH   SOLE   0 0 5,300
Becton Dickinson COM 075887109 18,149 71,748 SH   SOLE   0 0 71,748
Bellicum Pharmaceutica COM 079481107 12 11,270 SH   SOLE   0 0 11,270
Berkshire Hathaway Cl B COM 084670702 428 2,057 SH   SOLE   0 0 2,057
Black Stone Minerals L Com Uni COM 09225m101 2,853 200,357 SH   SOLE   0 0 200,357
Blackrock Inc COM 09247x101 263 590 SH   SOLE   0 0 590
Boeing Co. COM 097023105 471 1,238 SH   SOLE   0 0 1,238
CVS Health COM 126650100 9,769 154,887 SH   SOLE   0 0 154,887
Chevron Corp COM 166764100 3,053 25,743 SH   SOLE   0 0 25,743
Cisco Systems COM 17275R102 261 5,285 SH   SOLE   0 0 5,285
Coca-Cola COM 191216100 21,582 396,434 SH   SOLE   0 0 396,434
ConocoPhillips COM 20825C104 413 7,256 SH   SOLE   0 0 7,256
Donaldson COM 257651109 26,942 517,324 SH   SOLE   0 0 517,324
Dorchester Minerals LP COM 25820R105 978 52,423 SH   SOLE   0 0 52,423
Dover COM 260003108 21,475 215,702 SH   SOLE   0 0 215,702
Ecolab COM 278865100 33,776 170,551 SH   SOLE   0 0 170,551
Emerson Electric COM 291011104 17,760 265,624 SH   SOLE   0 0 265,624
Exxon Mobil Corp COM 30231g102 4,492 63,622 SH   SOLE   0 0 63,622
Facebook Inc Cl A COM 30303m102 321 1,800 SH   SOLE   0 0 1,800
FedEx COM 31428x106 15,989 109,839 SH   SOLE   0 0 109,839
First Financial Bankshares COM 32020R109 245 7,336 SH   SOLE   0 0 7,336
Home Depot Inc COM 437076102 513 2,212 SH   SOLE   0 0 2,212
Honeywell International COM 438516106 21,057 124,452 SH   SOLE   0 0 124,452
Illinois Tool Works COM 452308109 30,280 193,493 SH   SOLE   0 0 193,493
Intel COM 458140100 27,617 535,948 SH   SOLE   0 0 535,948
International Business Machine COM 459200101 468 3,218 SH   SOLE   0 0 3,218
Intuitive Surgical Inc Com New COM 46120E602 1,174 2,175 SH   SOLE   0 0 2,175
Ishares Tr S&P Midcap 400 COM 464287507 235 1,215 SH   SOLE   0 0 1,215
J.P. Morgan Chase & Co. COM 46625H100 565 4,799 SH   SOLE   0 0 4,799
Johnson & Johnson Com COM 478160104 22,976 177,585 SH   SOLE   0 0 177,585
Lam Research Corp. COM 512807108 337 1,459 SH   SOLE   0 0 1,459
Lockheed Martin Corp COM 539830109 236 604 SH   SOLE   0 0 604
Lowes Cos Inc COM 548661107 453 4,124 SH   SOLE   0 0 4,124
Luminex Corp COM 55027E102 666 32,270 SH   SOLE   0 0 32,270
Mastercard Inc Cl A COM 57636q104 1,249 4,598 SH   SOLE   0 0 4,598
McCormick COM 579780206 17,196 110,019 SH   SOLE   0 0 110,019
McDermott Intl Inc COM 580037109 57 28,270 SH   SOLE   0 0 28,270
McDonald's Corp. COM 580135101 256 1,192 SH   SOLE   0 0 1,192
Medtronic PLC COM g5960l103 823 7,576 SH   SOLE   0 0 7,576
Merck & Co Inc New COM 58933Y105 450 5,343 SH   SOLE   0 0 5,343
Microsoft COM 594918104 51,902 373,312 SH   SOLE   0 0 373,312
Mondelez Intl Inc Cl A COM 609207105 420 7,596 SH   SOLE   0 0 7,596
National Instr COM 636518102 20,296 483,363 SH   SOLE   0 0 483,363
Netflix Inc COM 64110L106 589 2,200 SH   SOLE   0 0 2,200
Nike Inc CL B COM 654106103 283 3,016 SH   SOLE   0 0 3,016
Nokia COM 654902204 77 15,250 SH   SOLE   0 0 15,250
Nordson COM 655663102 37,373 255,522 SH   SOLE   0 0 255,522
Novartis AG COM 66987V109 17,107 196,863 SH   SOLE   0 0 196,863
PNC Financial Services Group COM 693475105 286 2,043 SH   SOLE   0 0 2,043
Paccar COM 693718108 17,556 250,758 SH   SOLE   0 0 250,758
Paypal Hldgs Inc COM 70450Y103 340 3,280 SH   SOLE   0 0 3,280
PepsiCo COM 713448108 23,562 171,860 SH   SOLE   0 0 171,860
Pfizer, Inc. COM 717081103 271 7,550 SH   SOLE   0 0 7,550
Phillips 66 COM COM 718546104 623 6,081 SH   SOLE   0 0 6,081
Procter & Gamble COM 742718109 26,316 211,578 SH   SOLE   0 0 211,578
Sabine Royalty Trust UBI COM 785688102 607 14,000 SH   SOLE   0 0 14,000
Salesforce Com Inc COM 79466L302 297 2,000 SH   SOLE   0 0 2,000
San Juan Basin Royalty Trust COM 798241105 1,955 647,452 SH   SOLE   0 0 647,452
Schlumberger Ltd COM 806857108 5,975 174,864 SH   SOLE   0 0 174,864
Select Sector Spdr Tr Sbi Int- COM 81369y886 256 3,954 SH   SOLE   0 0 3,954
Sysco Corp COM 871829107 352 4,436 SH   SOLE   0 0 4,436
Taiwan Semiconductor COM 874039100 11,041 237,538 SH   SOLE   0 0 237,538
Telefonica de Espana COM 879382208 214 28,192 SH   SOLE   0 0 28,192
United Healthcare Corp COM 91324P102 419 1,927 SH   SOLE   0 0 1,927
United Parcel Svc Cl B COM 911312106 17,922 149,575 SH   SOLE   0 0 149,575
Vanguard FTSE Developed Market COM 921943858 230 5,596 SH   SOLE   0 0 5,596
Vanguard Index Fds Reit Viper COM 922908553 283 3,032 SH   SOLE   0 0 3,032
Vanguard World Fds Inf Tech ET COM 92204A702 415 1,924 SH   SOLE   0 0 1,924
Vanguard World Fds Materials E COM 92204A801 251 1,990 SH   SOLE   0 0 1,990
Verizon Communications COM 92343v104 365 6,050 SH   SOLE   0 0 6,050
W P Carey Inc COM 92936U109 208 2,326 SH   SOLE   0 0 2,326
Walt Disney COM 254687106 623 4,784 SH   SOLE   0 0 4,784
Waste Management Inc Del COM 94106L109 402 3,500 SH   SOLE   0 0 3,500