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 17,415 108,722 SH   SOLE   0 0 108,722
Abbott Labs COM 002824100 1,596 14,663 SH   SOLE   0 0 14,663
Abbvie Inc. Com COM 00287y109 1,316 15,021 SH   SOLE   0 0 15,021
Adobe Sys Inc COM 00724F101 381 776 SH   SOLE   0 0 776
Advanced Micro Devices COM 007903107 652 7,957 SH   SOLE   0 0 7,957
Air Prods & Chems COM 009158106 10,825 36,343 SH   SOLE   0 0 36,343
Alcon COM H01301128 11,403 200,236 SH   SOLE   0 0 200,236
Alphabet Inc Cap Sk Cl A COM 02079k305 932 636 SH   SOLE   0 0 636
Amazon.Com COM 023135106 13,961 4,434 SH   SOLE   0 0 4,434
Apple COM 037833100 40,270 347,721 SH   SOLE   0 0 347,721
Auto Data Processing COM 053015103 25,897 185,655 SH   SOLE   0 0 185,655
Becton Dickinson COM 075887109 16,765 72,050 SH   SOLE   0 0 72,050
Berkshire Hathaway Cl B COM 084670702 426 2,002 SH   SOLE   0 0 2,002
Black Stone Minerals L Com Uni COM 09225m101 923 150,357 SH   SOLE   0 0 150,357
Blackrock Inc COM 09247x101 332 590 SH   SOLE   0 0 590
CVS Health COM 126650100 237 4,066 SH   SOLE   0 0 4,066
Centene Corp Del COM 15135B101 227 3,885 SH   SOLE   0 0 3,885
Chevron Corp COM 166764100 569 7,899 SH   SOLE   0 0 7,899
Chipotle Mexican Grill Com COM 169656105 249 200 SH   SOLE   0 0 200
Cintas Corp Com COM 172908105 12,328 37,041 SH   SOLE   0 0 37,041
Coca-Cola COM 191216100 19,057 386,007 SH   SOLE   0 0 386,007
ConocoPhillips COM 20825C104 238 7,256 SH   SOLE   0 0 7,256
Donaldson COM 257651109 22,533 485,425 SH   SOLE   0 0 485,425
Dorchester Minerals LP COM 25820R105 542 52,423 SH   SOLE   0 0 52,423
Dover COM 260003108 22,099 203,976 SH   SOLE   0 0 203,976
Ecolab COM 278865100 30,796 154,103 SH   SOLE   0 0 154,103
Emerson Electric COM 291011104 16,839 256,805 SH   SOLE   0 0 256,805
Exxon Mobil Corp COM 30231g102 1,626 47,369 SH   SOLE   0 0 47,369
Facebook Inc Cl A COM 30303m102 528 2,016 SH   SOLE   0 0 2,016
FedEx COM 31428x106 28,000 111,323 SH   SOLE   0 0 111,323
First Financial Bankshares COM 32020R109 205 7,336 SH   SOLE   0 0 7,336
Home Depot Inc COM 437076102 604 2,176 SH   SOLE   0 0 2,176
Honeywell International COM 438516106 19,594 119,031 SH   SOLE   0 0 119,031
IShares Tr Trans Avg ETF COM 464287192 226 1,137 SH   SOLE   0 0 1,137
Illinois Tool Works COM 452308109 33,263 172,158 SH   SOLE   0 0 172,158
Intel COM 458140100 25,080 484,358 SH   SOLE   0 0 484,358
International Business Machine COM 459200101 456 3,747 SH   SOLE   0 0 3,747
Intuit COM 461202103 9,976 30,580 SH   SOLE   0 0 30,580
Intuitive Surgical COM 46120E602 12,024 16,946 SH   SOLE   0 0 16,946
Ishares Tr S&P Midcap 400 COM 464287507 246 1,326 SH   SOLE   0 0 1,326
J.P. Morgan Chase & Co. COM 46625H100 462 4,799 SH   SOLE   0 0 4,799
Johnson & Johnson COM 478160104 25,223 169,416 SH   SOLE   0 0 169,416
Lam Research Corp. COM 512807108 647 1,950 SH   SOLE   0 0 1,950
Lockheed Martin Corp COM 539830109 282 737 SH   SOLE   0 0 737
Lowes Cos Inc COM 548661107 668 4,030 SH   SOLE   0 0 4,030
Luminex Corp COM 55027E102 847 32,273 SH   SOLE   0 0 32,273
Mastercard Inc Cl A COM 57636q104 1,343 3,972 SH   SOLE   0 0 3,972
McCormick COM 579780206 19,399 99,945 SH   SOLE   0 0 99,945
McDonald's Corp. COM 580135101 251 1,142 SH   SOLE   0 0 1,142
Medtronic PLC COM g5960l103 806 7,757 SH   SOLE   0 0 7,757
Merck & Co Inc New COM 58933Y105 387 4,663 SH   SOLE   0 0 4,663
Microsoft COM 594918104 64,942 308,764 SH   SOLE   0 0 308,764
Mondelez Intl Inc Cl A COM 609207105 377 6,566 SH   SOLE   0 0 6,566
National Instr COM 636518102 15,662 438,701 SH   SOLE   0 0 438,701
Netflix Inc COM 64110L106 816 1,632 SH   SOLE   0 0 1,632
Nike Inc CL B COM 654106103 406 3,236 SH   SOLE   0 0 3,236
Nokia COM 654902204 60 15,250 SH   SOLE   0 0 15,250
Nordson COM 655663102 41,095 214,238 SH   SOLE   0 0 214,238
Novartis AG COM 66987V109 17,139 197,088 SH   SOLE   0 0 197,088
Nvidia COM 67066g104 211 390 SH   SOLE   0 0 390
Paccar COM 693718108 20,073 235,373 SH   SOLE   0 0 235,373
Paypal Hldgs Inc COM 70450Y103 696 3,530 SH   SOLE   0 0 3,530
PepsiCo COM 713448108 22,242 160,474 SH   SOLE   0 0 160,474
Procter & Gamble COM 742718109 27,332 196,646 SH   SOLE   0 0 196,646
Sabine Royalty Trust UBI COM 785688102 407 14,000 SH   SOLE   0 0 14,000
Salesforce Com Inc COM 79466L302 251 1,000 SH   SOLE   0 0 1,000
San Juan Basin Royalty Trust COM 798241105 1,625 647,452 SH   SOLE   0 0 647,452
ServiceNow Inc Com COM 81762P102 277 572 SH   SOLE   0 0 572
Shopify Inc Cl A COM 82509l107 205 200 SH   SOLE   0 0 200
Stryker COM 863667101 9,779 46,933 SH   SOLE   0 0 46,933
Sysco Corp COM 871829107 315 5,064 SH   SOLE   0 0 5,064
Taiwan Semiconductor COM 874039100 23,128 285,282 SH   SOLE   0 0 285,282
Telefonica de Espana COM 879382208 40 11,715 SH   SOLE   0 0 11,715
United Parcel Svc Cl B COM 911312106 5,499 33,003 SH   SOLE   0 0 33,003
UnitedHealth Group Inc COM 91324P102 601 1,927 SH   SOLE   0 0 1,927
Vanguard FTSE Developed Market COM 921943858 243 5,941 SH   SOLE   0 0 5,941
Vanguard World Fds Inf Tech ET COM 92204A702 599 1,924 SH   SOLE   0 0 1,924
Verizon Communications COM 92343v104 380 6,388 SH   SOLE   0 0 6,388
Visa Inc Cl A COM 92826c839 236 1,179 SH   SOLE   0 0 1,179
Walt Disney COM 254687106 253 2,037 SH   SOLE   0 0 2,037
Waste Management Inc Del COM 94106L109 396 3,500 SH   SOLE   0 0 3,500
Spdr Series Trust S&P Biotech COM 78464a870 388 3,482 SH   SOLE   0 0 3,482