Flora Unveiled

478 i Flora Unveiled

valuable particulars, shedding new light on the most diverse problems of the cell-

theory and of morphology, was lost in the splendor of the total result.^2

Sachs pointed out that Hofmeister’s grand synthesis was incompatible with the prevail-
ing idea of the fixity of species:

The reader of Hofmeister’s “Comparative Investigations” was presented with a picture

of genetic affinity between Cryptogams and Phanerogams [seed plants], which could

not be reconciled with the then reigning belief in the fixity of species. He was invited

to recognize a connection of development which made the most different things

appear to be closely united together, the simplest Moss with Palms, Conifers, and

angiospermous trees, and which was incompatible with the theory of original types.^3

After Hofmeister, Sachs declared, the so- called natural systems of classification had to be
revised along evolutionary lines. Indeed, Hofmeister’s research had prepared the ground for
Da r w i n’s Origin of Species:^4

The assumption that every natural group represents a [Divine] idea was here quite out

of place; the notion entertained up to that time of what was really meant by the natural

system had to be entirely altered. ... When Darwin’s theory was given to the world

eight years after Hofmeister’s investigations, the relations of affinity between the great

divisions of the vegetable kingdom were so well established and so patent, that the

theory of descent had only to accept what morphology had actually brought to view.^5

Hofmeister’s Central Insight

The concept of alternation of generations in plant life cycles has earned the reputation
among plant biology instructors of being exceptionally hard to teach. And yet it is concep-
tually quite simple. The source of the pedagogical problem is fairly obvious: humans are ani-
mals, with typical animal life cycles. We naturally associate sexuality with the adult stage
of the life cycle. This zoocentric idea of sexuality biases our expectations about sexuality
in plants. When we look at, say, a fiddlehead fern, we feel that this large, elegant, mature
individual must be the adult stage of the organism and therefore the sexual stage of the life
cycle. But it isn’t!
When we turn over a fern frond, we see clusters of sporangia filled with spores. They
look something like seeds. Seeds, we know, contain the embryos of the next generation.
We assume that if we place these spores on the ground, they will grow directly into another
spore- producing fiddlehead fern plant. But they don’t! As we have seen, fern spores germi-
nate to form a totally different kind of plant called a prothallus, which is much smaller and
simpler than the “parent” fern. Contrary to our expectations, it is the diminutive prothallus
that bears the sexual organs: archegonia and antheridia. Counterintuitively, this tiny pro-
thallus, which looks more like a humble liverwort than a venerable fern plant, is the mature
sexual stage of the fern. The large, elegant organism we think of as the “fiddlehead fern” is
actually the asexual spore- producing generation of the life cycle. It is the inconspicuous and