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 22,326 112,400 SH   SOLE   0 0 112,400
Abbott Labs COM 002824100 1,702 14,682 SH   SOLE   0 0 14,682
Abbvie Inc. Com COM 00287y109 1,698 15,078 SH   SOLE   0 0 15,078
Adobe Sys Inc COM 00724F101 470 802 SH   SOLE   0 0 802
Advanced Micro Devices COM 007903107 878 9,346 SH   SOLE   0 0 9,346
Air Prods & Chems COM 009158106 11,997 41,703 SH   SOLE   0 0 41,703
Alcon COM H01301128 14,926 212,438 SH   SOLE   0 0 212,438
Alphabet Inc Cap Sk Cl A COM 02079k305 1,658 679 SH   SOLE   0 0 679
Alphabet Inc Cap Sk Cl C COM 02079k107 298 119 SH   SOLE   0 0 119
Amazon.Com COM 023135106 16,241 4,721 SH   SOLE   0 0 4,721
Apple COM 037833100 48,600 354,851 SH   SOLE   0 0 354,851
Applied Materials Inc COM 038222105 228 1,600 SH   SOLE   0 0 1,600
Auto Data Processing COM 053015103 37,071 186,642 SH   SOLE   0 0 186,642
Becton Dickinson COM 075887109 18,508 76,104 SH   SOLE   0 0 76,104
Berkshire Hathaway Cl B COM 084670702 556 2,002 SH   SOLE   0 0 2,002
Black Stone Minerals L Com Uni COM 09225m101 1,616 150,357 SH   SOLE   0 0 150,357
Blackrock Inc COM 09247x101 516 590 SH   SOLE   0 0 590
Blackstone Group Inc. COM 09253u108 444 4,575 SH   SOLE   0 0 4,575
CVS Health COM 126650100 297 3,562 SH   SOLE   0 0 3,562
Centene Corp Del COM 15135B101 284 3,895 SH   SOLE   0 0 3,895
Charter Communications Cl A COM 16119p108 207 287 SH   SOLE   0 0 287
Chevron Corp COM 166764100 973 9,290 SH   SOLE   0 0 9,290
Chipotle Mexican Grill Com COM 169656105 310 200 SH   SOLE   0 0 200
Cintas Corp Com COM 172908105 15,439 40,415 SH   SOLE   0 0 40,415
Coca-Cola COM 191216100 21,625 399,645 SH   SOLE   0 0 399,645
ConocoPhillips COM 20825C104 545 8,945 SH   SOLE   0 0 8,945
Costco Wholesale Corp New COM 22160k105 201 508 SH   SOLE   0 0 508
Danaher Corp COM 235851102 200 746 SH   SOLE   0 0 746
Donaldson COM 257651109 31,300 492,681 SH   SOLE   0 0 492,681
Dorchester Minerals LP COM 25820R105 883 52,423 SH   SOLE   0 0 52,423
Dover COM 260003108 31,212 207,250 SH   SOLE   0 0 207,250
Ecolab COM 278865100 32,128 155,982 SH   SOLE   0 0 155,982
Emerson Electric COM 291011104 25,109 260,899 SH   SOLE   0 0 260,899
Exxon Mobil Corp COM 30231g102 2,931 46,466 SH   SOLE   0 0 46,466
Facebook Inc Cl A COM 30303m102 766 2,204 SH   SOLE   0 0 2,204
FedEx COM 31428x106 33,443 112,101 SH   SOLE   0 0 112,101
First Financial Bankshares COM 32020R109 360 7,336 SH   SOLE   0 0 7,336
Home Depot Inc COM 437076102 579 1,814 SH   SOLE   0 0 1,814
Honeywell International COM 438516106 26,453 120,596 SH   SOLE   0 0 120,596
IShares Tr Trans Avg ETF COM 464287192 296 1,140 SH   SOLE   0 0 1,140
Illinois Tool Works COM 452308109 38,589 172,611 SH   SOLE   0 0 172,611
Intel COM 458140100 27,613 491,867 SH   SOLE   0 0 491,867
International Business Machine COM 459200101 493 3,365 SH   SOLE   0 0 3,365
Intuit COM 461202103 16,284 33,222 SH   SOLE   0 0 33,222
Intuitive Surgical COM 46120E602 16,935 18,415 SH   SOLE   0 0 18,415
Ishares Tr S&P Midcap 400 COM 464287507 356 1,326 SH   SOLE   0 0 1,326
J.P. Morgan Chase & Co. COM 46625H100 750 4,820 SH   SOLE   0 0 4,820
Johnson & Johnson COM 478160104 28,539 173,239 SH   SOLE   0 0 173,239
Lam Research Corp. COM 512807108 1,307 2,008 SH   SOLE   0 0 2,008
Lockheed Martin Corp COM 539830109 281 742 SH   SOLE   0 0 742
Lowes Cos Inc COM 548661107 782 4,033 SH   SOLE   0 0 4,033
Luminex Corp COM 55027E102 1,188 32,275 SH   SOLE   0 0 32,275
Mastercard Inc Cl A COM 57636q104 1,552 4,251 SH   SOLE   0 0 4,251
McCormick COM 579780206 18,436 208,745 SH   SOLE   0 0 208,745
McDonald's Corp. COM 580135101 264 1,142 SH   SOLE   0 0 1,142
Medtronic PLC COM g5960l103 979 7,887 SH   SOLE   0 0 7,887
Merck & Co Inc New COM 58933Y105 376 4,833 SH   SOLE   0 0 4,833
Microsoft COM 594918104 83,325 307,585 SH   SOLE   0 0 307,585
Mondelez Intl Inc Cl A COM 609207105 413 6,610 SH   SOLE   0 0 6,610
National Instr COM 636518102 18,919 447,477 SH   SOLE   0 0 447,477
Netflix Inc COM 64110L106 888 1,682 SH   SOLE   0 0 1,682
Nike Inc CL B COM 654106103 395 2,559 SH   SOLE   0 0 2,559
Nokia COM 654902204 69 13,000 SH   SOLE   0 0 13,000
Nordson COM 655663102 47,386 215,873 SH   SOLE   0 0 215,873
Novartis AG COM 66987V109 18,797 206,020 SH   SOLE   0 0 206,020
Nvidia COM 67066g104 390 488 SH   SOLE   0 0 488
Paccar COM 693718108 21,519 241,111 SH   SOLE   0 0 241,111
Paypal Hldgs Inc COM 70450Y103 1,116 3,830 SH   SOLE   0 0 3,830
PepsiCo COM 713448108 24,415 164,774 SH   SOLE   0 0 164,774
Phillips 66 COM COM 718546104 317 3,688 SH   SOLE   0 0 3,688
Procter & Gamble COM 742718109 27,010 200,176 SH   SOLE   0 0 200,176
S&P Global Inc COM 78409v104 214 521 SH   SOLE   0 0 521
Sabine Royalty Trust UBI COM 785688102 564 14,000 SH   SOLE   0 0 14,000
Salesforce Com Inc COM 79466L302 683 2,796 SH   SOLE   0 0 2,796
San Juan Basin Royalty Trust COM 798241105 2,905 565,191 SH   SOLE   0 0 565,191
ServiceNow Inc Com COM 81762P102 314 572 SH   SOLE   0 0 572
Shopify Inc Cl A COM 82509l107 314 215 SH   SOLE   0 0 215
Stryker COM 863667101 13,426 51,693 SH   SOLE   0 0 51,693
Sysco Corp COM 871829107 394 5,072 SH   SOLE   0 0 5,072
Taiwan Semiconductor COM 874039100 34,357 285,930 SH   SOLE   0 0 285,930
Target COM 87612e106 231 955 SH   SOLE   0 0 955
Telefonica de Espana COM 879382208 61 12,983 SH   SOLE   0 0 12,983
Tractor Supply Co COM 892356106 206 1,109 SH   SOLE   0 0 1,109
United Parcel Svc Cl B COM 911312106 5,702 27,420 SH   SOLE   0 0 27,420
UnitedHealth Group Inc COM 91324P102 824 2,057 SH   SOLE   0 0 2,057
Vanguard FTSE Developed Market COM 921943858 306 5,941 SH   SOLE   0 0 5,941
Vanguard Intl Eqty Idx Emr Mkt COM 922042858 239 4,409 SH   SOLE   0 0 4,409
Vanguard World Fds Inf Tech ET COM 92204A702 253 634 SH   SOLE   0 0 634
Walt Disney COM 254687106 493 2,802 SH   SOLE   0 0 2,802
Waste Management Inc Del COM 94106L109 490 3,500 SH   SOLE   0 0 3,500
Workday Inc Cl A COM 98138h101 217 911 SH   SOLE   0 0 911
Spdr Series Trust S&P Biotech COM 78464a870 471 3,482 SH   SOLE   0 0 3,482