SEXUAL REPRODUCTION OF THALLOPHYTES. 299 
Micheli described the apothecia of Lichens as flowers, 
and the asci as stamens. Hedwig (1783) laid the foundation 
of an accurate knowledge of the sexual reproduction of 
mosses, but thought that the function of anthers was per- 
formed in Ferns by the hairs on the back of the midrib of 
the fronds, while in Fungi it was accomplished by the 
velum. 
Such views, as Decaisne and Thuret pointed out in 
writing on the reproduction of Fucus, being based only 
upon hypothesis or imperfect observations, fell later on 
into deserved neglect. A reaction began against the ap- 
plication of the doctrine of sexuality to the lower plants. 
Gmelin (1760) thought that in descending through the 
vegetable series the diversity of the sexes gradually dimin- 
ished, till in Fuci a point was reached where fructi- 
fication took place without fertilization at all. Gaertner 
(1788) held that the spores of the greater part of the alge 
(including the Floridez) were not true seeds, but “‘ gemme.” 
In Fucus he believed that the ‘‘ uterus” (conceptacle) 
accomplished the fertilisation of the enclosed spores.! 
At the beginning of the present century the reaction 
against the belief in the sexuality of the lower plants 
reached its climax. Endlicher made the absence of sexes, 
as has already been noticed, one of the distinguishing marks 
of Thallophytes ; Schleiden, in his ‘Grundzuge’ (1845), 
ignores, as far as possible, any facts which seem to point 
to the existence of sexuality amongst them. But even 
Schleiden could not have shut his eyes to actual demonstra- 
tion, and his attitude shows that the sexuality of the Thal- 
lophytes up to his time had, in reality, been rather inferred 
than actually proved. The whole of our present knowledge, 
in fact, rests on the researches of the last thirty years. 
Linneeus first made use of reproductive organs as a basis 
of classification in his ‘Systema 4 Sexu’ published in 1735. 
Sprengel? remarks that, a little while before this, when 
only twenty-three years old, “lectione Vaillantii et Blairii 
incensus sexualis systematis fundamenta ponere ccepit.” 
In its essential features sexual reproduction implies the fu- 
sion of two individualised particles of protoplasm. De Bary 
(1858) was the first to point out in his memoir on the Conjugate 
that this process exists in its most generalised form in “ con- 
jugation.” This phenomenon had long been known in the 
1“ Palam est .... quod in Fucis genuinis .... ipse uterus sua foecun- 
det ovula, et quod ille ipse, officia genitalium utriusque sexts, prestet 
solus” (‘ De Fructibus,’ p. xxxiii). 
2 * Historia,’ vol. ii, p. 323. 
