Martin (1992: 104):
For similar reasons, generic groups may neutralise number. Note that in [3:17] a thick waterproof covering could be replaced with thick waterproof coverings without necessarily implying that cacti have more than one layer or kind of covering to protect their pulpy cells. Similarly animals can be substituted with an animal (or to return to the question of definiteness the animals for that matter) without significantly affecting the meaning of the text.
The cacti have extensive root systems spreading in all directions — sideways and downwards — to soak up as much water as possible when it rains. They are able to swell to store water, and they then use this water over long periods of drought. A thick waterproof covering protects these desert water-tanks with their soft pulpy cells, and their leaves are often reduced to thorns to cut down on water-loss and protect the plant from animals that might otherwise eat it for its moisture.These neutralisations affect the nature of cohesive patterns in texts oriented to generic classes of participant; pronouns and demonstratives are commonly used to presume generic participants, but the is not phoric in generic contexts. This has the effect of breaking up the participant line into a number of short generic reference chains. … Note that when qualified, pronouns can themselves be used generically: He who hesitates is lost. These pronouns simply point forward to their Qualifier and do not in themselves presume generic participants.
 This unsupported claim is falsified in text [3:17] by the cacti, where the is either homophoric, if this is the first instance of cacti, or more likely, anaphoric to a previous instance in the preceding (unquoted) co-text, and so: endophoric and cohesive.
 This is not true, even in cases where the is not endophoric and cohesive, since any subsequent reference item will also link back to the referent in question, thereby continuing the chain.
 The simultaneous claims here are that such pronouns:
- can be used generically
- do not presume generic participants.
 To be clear, he refers to the member of a class, not to the generic class itself.
 To be clear, in SFL terms, this personal co-reference of he is cataphoric, but structural rather than cohesive, since 'the reference is resolved within the nominal group where the reference item appears' (Halliday & Matthiessen 2014: 625).