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 21,494 111,551 SH   SOLE   0 0 111,551
Abbott Labs COM 002824100 1,759 14,675 SH   SOLE   0 0 14,675
Abbvie Inc. Com COM 00287y109 1,635 15,104 SH   SOLE   0 0 15,104
Adobe Sys Inc COM 00724F101 368 774 SH   SOLE   0 0 774
Advanced Micro Devices COM 007903107 720 9,167 SH   SOLE   0 0 9,167
Air Prods & Chems COM 009158106 11,250 39,988 SH   SOLE   0 0 39,988
Alcon COM H01301128 14,522 206,928 SH   SOLE   0 0 206,928
Alphabet Inc Cap Sk Cl A COM 02079k305 1,407 682 SH   SOLE   0 0 682
Alphabet Inc Cap Sk Cl C COM 02079k107 246 119 SH   SOLE   0 0 119
Amazon.Com COM 023135106 14,508 4,689 SH   SOLE   0 0 4,689
Apple COM 037833100 43,077 352,661 SH   SOLE   0 0 352,661
Applied Materials Inc COM 038222105 214 1,600 SH   SOLE   0 0 1,600
Auto Data Processing COM 053015103 35,200 186,768 SH   SOLE   0 0 186,768
Becton Dickinson COM 075887109 18,095 74,421 SH   SOLE   0 0 74,421
Berkshire Hathaway Cl B COM 084670702 511 2,002 SH   SOLE   0 0 2,002
Black Stone Minerals L Com Uni COM 09225m101 1,311 150,357 SH   SOLE   0 0 150,357
Blackrock Inc COM 09247x101 445 590 SH   SOLE   0 0 590
Blackstone Group Inc. COM 09253u108 341 4,575 SH   SOLE   0 0 4,575
CVS Health COM 126650100 268 3,562 SH   SOLE   0 0 3,562
Centene Corp Del COM 15135B101 249 3,895 SH   SOLE   0 0 3,895
Chevron Corp COM 166764100 973 9,281 SH   SOLE   0 0 9,281
Chipotle Mexican Grill Com COM 169656105 284 200 SH   SOLE   0 0 200
Cintas Corp Com COM 172908105 13,386 39,220 SH   SOLE   0 0 39,220
Coca-Cola COM 191216100 20,888 396,279 SH   SOLE   0 0 396,279
ConocoPhillips COM 20825C104 384 7,256 SH   SOLE   0 0 7,256
Donaldson COM 257651109 28,575 491,320 SH   SOLE   0 0 491,320
Dorchester Minerals LP COM 25820R105 716 52,423 SH   SOLE   0 0 52,423
Dover COM 260003108 28,424 207,281 SH   SOLE   0 0 207,281
Ecolab COM 278865100 33,376 155,910 SH   SOLE   0 0 155,910
Emerson Electric COM 291011104 23,472 260,168 SH   SOLE   0 0 260,168
Exxon Mobil Corp COM 30231g102 2,609 46,731 SH   SOLE   0 0 46,731
Facebook Inc Cl A COM 30303m102 657 2,232 SH   SOLE   0 0 2,232
FedEx COM 31428x106 31,806 111,979 SH   SOLE   0 0 111,979
First Financial Bankshares COM 32020R109 343 7,336 SH   SOLE   0 0 7,336
Home Depot Inc COM 437076102 644 2,110 SH   SOLE   0 0 2,110
Honeywell International COM 438516106 26,127 120,363 SH   SOLE   0 0 120,363
IShares Tr Trans Avg ETF COM 464287192 294 1,140 SH   SOLE   0 0 1,140
Illinois Tool Works COM 452308109 38,235 172,603 SH   SOLE   0 0 172,603
Intel COM 458140100 31,232 488,007 SH   SOLE   0 0 488,007
International Business Machine COM 459200101 448 3,365 SH   SOLE   0 0 3,365
Intuit COM 461202103 12,453 32,509 SH   SOLE   0 0 32,509
Intuitive Surgical COM 46120E602 13,265 17,952 SH   SOLE   0 0 17,952
Ishares Tr S&P Midcap 400 COM 464287507 345 1,326 SH   SOLE   0 0 1,326
J.P. Morgan Chase & Co. COM 46625H100 734 4,820 SH   SOLE   0 0 4,820
Johnson & Johnson COM 478160104 28,373 172,635 SH   SOLE   0 0 172,635
Lam Research Corp. COM 512807108 1,210 2,032 SH   SOLE   0 0 2,032
Lockheed Martin Corp COM 539830109 274 742 SH   SOLE   0 0 742
Lowes Cos Inc COM 548661107 767 4,032 SH   SOLE   0 0 4,032
Luminex Corp COM 55027E102 1,030 32,275 SH   SOLE   0 0 32,275
Mastercard Inc Cl A COM 57636q104 1,514 4,251 SH   SOLE   0 0 4,251
McCormick COM 579780206 18,381 206,163 SH   SOLE   0 0 206,163
McDonald's Corp. COM 580135101 256 1,142 SH   SOLE   0 0 1,142
Medtronic PLC COM g5960l103 928 7,852 SH   SOLE   0 0 7,852
Merck & Co Inc New COM 58933Y105 363 4,710 SH   SOLE   0 0 4,710
Microsoft COM 594918104 72,702 308,361 SH   SOLE   0 0 308,361
Mondelez Intl Inc Cl A COM 609207105 387 6,610 SH   SOLE   0 0 6,610
National Instr COM 636518102 19,251 445,781 SH   SOLE   0 0 445,781
Netflix Inc COM 64110L106 877 1,682 SH   SOLE   0 0 1,682
Nike Inc CL B COM 654106103 434 3,265 SH   SOLE   0 0 3,265
Nokia COM 654902204 51 13,000 SH   SOLE   0 0 13,000
Nordson COM 655663102 42,936 216,104 SH   SOLE   0 0 216,104
Novartis AG COM 66987V109 17,366 203,159 SH   SOLE   0 0 203,159
Nvidia COM 67066g104 276 516 SH   SOLE   0 0 516
Paccar COM 693718108 22,261 239,574 SH   SOLE   0 0 239,574
Paypal Hldgs Inc COM 70450Y103 930 3,830 SH   SOLE   0 0 3,830
PepsiCo COM 713448108 23,209 164,078 SH   SOLE   0 0 164,078
Phillips 66 COM COM 718546104 301 3,688 SH   SOLE   0 0 3,688
Procter & Gamble COM 742718109 27,049 199,728 SH   SOLE   0 0 199,728
Sabine Royalty Trust UBI COM 785688102 425 14,000 SH   SOLE   0 0 14,000
Salesforce Com Inc COM 79466L302 527 2,489 SH   SOLE   0 0 2,489
San Juan Basin Royalty Trust COM 798241105 2,238 565,191 SH   SOLE   0 0 565,191
ServiceNow Inc Com COM 81762P102 286 572 SH   SOLE   0 0 572
Shopify Inc Cl A COM 82509l107 243 220 SH   SOLE   0 0 220
Stryker COM 863667101 12,204 50,103 SH   SOLE   0 0 50,103
Sysco Corp COM 871829107 399 5,070 SH   SOLE   0 0 5,070
Taiwan Semiconductor COM 874039100 33,783 285,615 SH   SOLE   0 0 285,615
Telefonica de Espana COM 879382208 56 12,366 SH   SOLE   0 0 12,366
United Parcel Svc Cl B COM 911312106 5,320 31,298 SH   SOLE   0 0 31,298
UnitedHealth Group Inc COM 91324P102 761 2,045 SH   SOLE   0 0 2,045
Vanguard FTSE Developed Market COM 921943858 292 5,941 SH   SOLE   0 0 5,941
Vanguard Intl Eqty Idx Emr Mkt COM 922042858 229 4,409 SH   SOLE   0 0 4,409
Vanguard World Fds Inf Tech ET COM 92204A702 227 634 SH   SOLE   0 0 634
Walt Disney COM 254687106 517 2,802 SH   SOLE   0 0 2,802
Waste Management Inc Del COM 94106L109 452 3,500 SH   SOLE   0 0 3,500
Workday Inc Cl A COM 98138h101 226 911 SH   SOLE   0 0 911
Spdr Series Trust S&P Biotech COM 78464a870 472 3,482 SH   SOLE   0 0 3,482