Sentences with two subjects separated by “and” can be ambiguous when the first subject contains a prepositional phrase. Here’s an example I ran across recently in a chemistry paper I was editing:
Data processing for reproduction of element maps and calculation of fluorescence counts was performed with the software package.
The presence of the “for” phrase introduces ambiguity. What was performed with the software? Just the data processing, as implied by the use of the singular verb form “was”? Or did the author mean that the software was used for data processing and for calculation. That is, did the author mean
Data processing . . . and calculation . . . were performed with the software package.
rather than
Data processing for reproduction . . . and for calculation . . . was performed with the software package.
You might argue that readers familiar with the functionality of the software package, or with element maps and fluorescence counts, will probably know immediately that only one of these meanings make sense. Why take the chance though? Why not make your meaning completely unambiguous? To do so, you’ve got a couple options. If you mean the subject to be singular, you can repeat the preposition:
Data processing for reproduction of element maps and for calculation of fluorescence counts was performed with the software package.
If you mean the subject to be plural, the revision will have to be a little more extensive. Sometimes simply changing the order of the two subjects will work:
Calculation of fluorescence counts and data processing for reproduction of element maps were performed with the software package.
Because both subjects in this particular sentence contain prepositional phrases, you might also want to go further and eliminate the “of” phrase:
Fluorescence count calculation and data processing for reproduction of element maps were performed with the software package.
If you can’t fix the problem by changing the word order, try supplying an actor and using the active voice:
We used the software package to process data for reproduction of element maps and to calculate fluorescence counts.
Here’s another, more-complex sentence:
Node I, the culms between node I and the rachis, the flag leaf blade, and the panicle were dried separately.
Readers who, like me, are a bit shaky on their plant anatomy might momentarily wonder whether “the culms between node I and” applies to “the rachis” alone or whether the author means
Node I and the culms between node I and the rachis, [the culms between node I and] the flag leaf blade, and [the culms between node I and] the panicle were dried separately.
Are there four subjects (node I, culms, blade, and panicle) or only two (node I and culms)? If there are only two, you can clarify by repeat the preposition “between”:
Node I and the culms between node I and the rachis, between node I and the flag leaf blade, and between node I and the panicle were dried separately.
If there are four, the easiest solution is to change the commas to semicolons:
Node I; the culms between node I and the rachis; the flag leaf blade; and the panicle were dried separately.
You can also change the order of the items in the list so that the item with the prepositional phrase comes last:
Node I, the flag leaf blade, the panicle, and the culms between node I and the rachis were dried separately.
As I said in my previous post, be kind to newbies. “Part of what the editor or self-editor must do . . . is to approach the text as a stranger might. . . . a good edit must involve the kind of skeptical reading in which one imagines how one reader in ten might misread the sentence” (Garner’s Modern American Usage, 3rd ed. [Oxford: Oxford University Press, 2009], s.v. “Miscues”).