This is an action to recover damages alleged to have been caused to a erop growing on plaintiffs’ land. Plaintiffs allege that defendant applied a chemical *594spray to brush and weeds on its property in such a manner as to cause drops of chemical spray and vapors to fall on plaintiffs’ land, resulting in damage to plaintiffs’ crop of pole beans. The jury returned a verdict in favor of defendant and plaintiffs appeal.
Plaintiffs contend that the trial court erred in admitting into evidence a series of photographs on the ground that they were not authenticated or verified and in permitting defendant’s expert to express his opinion as to the cause of the injury to plaintiffs’ beans on the ground that the opinion was not based upon facts in evidence.
The photographs in question, purporting to depict the appearance of the damaged pole beans, were admitted in evidence through the testimony of defendant Otto Paeschke. Paeschke testified that he did not take the photographs himself and that he was not present and did not know when or by whom they had been taken. He also testified that he did not know whether the photographs were of beans in plaintiffs’ field. However, he stated that he had been in plaintiffs’ field in August, 1970, when the damage had been reported, and had seen the beans there. He then testified that “the condition in the pictures is the. same condition as I saw in my examination of the field.” The trial court admitted the photographs over plaintiffs’ objection.
The basis of plaintiffs’ objection was that the foundation of Paeschke’s identification and verification was insufficient to render the photographs admissible. This claim is without merit. The purpose of the photographs was merely to help the witness describe the beans which he observed in plaintiffs’ field by comparing them with the beans shown in the photographs. The *595photographs constituted demonstrative evidence and as such they were relevant and admissible in the same way that a map, chart or drawing should be admissible.
Plaintiffs’ second contention is that defendant’s expert should not have been permitted to testify because the witness based his opinion on facts not in evidence. The rule is ordinarily stated that an expert witness’s opinion must be based upon facts in evidence. This statement of the rule is too broad, as is demonstrated by State Highway Comm. v. Arnold, 218 Or 43, 341 P2d 1089, 343 P2d 1113 (1959).① However, it is not necessary for us to explore the boundaries of the rule because all of the material facts relied upon by defendant’s witness were in evidence in this case, as appears from the following discussion.
Defendant called as a witness Dr. Virgil Freed, a professor of chemistry at Oregon State University. Dr. Freed stated that in reaching his opinion he relied upon three sources of inf ormation: (1) the photographs discussed above; (2) a report in the form of a letter prepared by plaintiffs’ expert, Mr. Thomas Harrison, an agronomist employed by the State Department of Agriculture; and (3) a “brochure” describing the kind of chemical used by defendant in spraying its land.
Mr. Harrison’s report had earlier been offered in evidence by plaintiffs but was excluded because one part of it was hearsay. Mr. Harrison then testified. It is clear from the record and a comparison with the excluded *596report that Mr. Harrison testified to the same facts and explanation that were contained in his report.②
When called as a witness, Dr. Freed testified that he did not rely on the hearsay portion of the report and that its presence did not affect his opinion. In *597these circumstances, Dr. Freed’s statement that he relied on a written report was tantamount to saying that he relied on the evidence presented by Mr. Harrison at trial. The trial court was therefore justified in permitting Dr. Freed to testify in reliance upon that report.③
*598The plaintiffs also contend that the “brochure” was not in evidence. Defendant did introduce a document referred to as a “specimen label.” Paeschke testified that that document identified the kind of spray he used in spraying the weeds on his property. Dr. Freed testified that a document which he denoted as a “brochure” similarly described the spray. Both stated that the document identified the same chemical compound that Mr. Harrison had discussed in his report and which he testified was that which probably had been used on defendant’s field. Moreover, examination of the “specimen label” in evidence reveals that its obverse side constituted a “brochure.”④ Whether the specimen label was the brochure referred to by the witness is a question of fact.
When the admissibility of evidence depends upon the determination of questions of fact, the trial court decides such questions. McCormick on Evidence 121 (2d ed 1972). Sometimes special findings are made. Farmers’ Bank v. Woodell, 38 Or 294, 61 P 837, 65 P 520 (1900). Frequently no special findings are made and it is inferred that the trial court made fact findings consistent with its ruling on the admissibility of the evidence. Bdwy. Finance, Inc. v. Tadorovich et al, 216 Or 475, 478, 339 P2d 436 (1959); Blue v. City of Union, 159 Or 5, 75 P2d 977 (1938).⑤ This same inference is *599also applicable to support the trial court’s treatment of the contents of the report as having been introduced into evidence and thus constituting a basis for Dr. Freed’s expert opinion.
Judgment affirmed.
Contrary to the suggestion found in the dissenting opinion, the hearsay statements which the expert used in making his evaluation were not in evidence in State Highway Comm v. Arnold, supra. Thus, the case does stand as a clear exception to the “facts in evidence” rule. See also Wulff v. Sprouse-Reitz Co., Inc., 262 Or 293, 498 P2d 766 (1972).
Mr. Harrison’s written report read as follows:
“Lloyd Harpole
“A portion of the early planting of pole beans show distorted foliage which is associated with an characteristic of exposure to one of the growth regulator herbicides such as 2,4-D, 2,45T, etc.
“The attached sketch shows the general area affected. The exposure was fairly uniform throughout the area except along the line of demarcation where here plants showed a gradual change to normal foliage. All of the plants were not showing distorted growth within the exposed area. It was possible to find normal plants adjacent to plants showing severe distortion. A typical drift pattern was not exemplified in this field as it was found the severity was no greater along the north end as compared to plants further south. The degree of exposure was fairly uniform.
“T.B.A. was undetectable in soil samples which were taken from your field in question and were submitted to Oregon State University for residue analysis. A Biosassay proved negative to growth regulators.”
The last paragraph constituted the inadmissible hearsay and may be disregarded.
Excerpts from Mr. Harrison’s testimony:
“Q. * * * [A]s a result of your observations, examination, you wrote a letter to Mr. Harpole giving him your findings, didn’t you?
“A. Yes.
“Q. * * * [I]ts a three paragraph letter addressed to Lloyd Harpole.
“A. Yes.
(($ $ $
“Q. Now, your comment then, referring to the first paragraph, is that a portion of the early planting of pole beans shows distorted foliage which is associated and a characteristic of exposure to one of the growth regulator herbicides such as 2-4D, 2,4,5-T, etcetera.
Is that the statement you made to him?
“A. That’s correct.
*597(($ $ ‡ ‡ $
“Q. What area of the field was that damage located in?
“A. In 1970 it was in the northern — northern corner. Northeast corner.
“Q. Now, your testimony was that there was equal — appeared to be equal exposure throughout the affected area?
“A. Yes. In other words, the plants from the north end to the south end, provided you didn’t get into the demarcation line, there was a line that ran from injured plants to no injured plants.
«3: % %
“Q. It was referred to as the Harpole report. Report to the Harpoles.
Maybe if I quote you a portion of that letter that was quoted by Mr. Gidley you can find the letter. It read, ‘The exposure was fairly uniform throughout the area except the line of demarcation. All of the plants were not showing distorted growth within the exposed area. It was possible to find normal plants next to plants showing severe distortion.’ You have that letter?
“A. Yes, that’s the report of my findings in response to the complaint filed by Lloyd Harpole.
CC$ * * * *
“Q. * * * I am referring again to your report to Mr. Harpole that I talked about earlier. You said a typical drift pattern was not exemplified in this field as it was found the severity was not greater along the north end as compared to plants further south. * * * [I]f the pattern had been typical on the south end of the afflicted area there would have been less injury?
“A. Yes.
“Q. Okay. If there had been a spray here which had affected the beans, typically, you would have expected to find what you just described as typical drift pattern and your note indicates that in this case you did not find that?
“A. Correct.”
Wulff v. Sprouse-Reitz Co., Inc., 262 Or 293, 498 P2d 766 (1972).
Indeed, it is interesting to note that the trial clerk’s record list identifies this document as a brochure,
The purpose of Rule 56 (3) of the Uniform Rules of Evidence may be to approve the making of such inferences in the absence of special findings. Butler, How the Adoption of the Uniform Rules of Evidence Would Affect the Law of Evidence in Oregon: Rules 56-61, 42 Ór L Rev 181, 187-89 (1963): Rule 56 (3) provides: “Unless the judge excludes the [expert] testimony he shall be deemed to have made the finding requisite to its admission.” Uniform Rules of Evidence, Rule 56 (3), 9A ULA.630 (1965). .
*599The “requisite” finding is set out in Rule 56 (2), which states: “If the witness is testifying as an expert, testimony of the witness in- the form of opinions or inferences is limited to such opinions as the judge finds are (a) based on facts or data perceived by or personally known or made known to the witness at the hearing, and (b) within the scope of the special knowledge, skill, experience or training possessed by the witness.” Uniform Rules of Evidence, Rule 56 (2), 9A ULA 630 (1965).