1881. ] by the Flistery of Sex in Plants. gt 
tions are to be found. The purely asexual state exists only in the 
lowest Protophytes, as in Saccharomyces, the Phycochromacee, 
and other unicellular forms. The simple phenomenon of conju- 
gation or copulation seen in the Zygomycete and diatoms, forms 
the earliest step towards sexual differentiation, which is followed 
by the various intermediate steps represented by the pairing of 
active cells in Volvox, the formation of odspores in the Conferve 
and Fucacez, and of carpospores in the Fungi. 
In the Characez we first find the well marked distinction of 
antheridia and carpogonia, the former furnishing in Nitella the 
active spermatozodids which differ immensely from the cells with 
which they combine. This latter feature continues to character- 
ize all the higher Cryptogams, though in nearly all cases the 
organs of both sexes are borne on the same plant. The transition 
from the Cryptogams to the Phanerogams is effected by a primary 
differentiation of the spores, which in most Cryptogams are the 
independent asexual bodies that produce the sexually differentiated 
prothallium. This prothallium loses its independence and be- 
comes the albumen of the seed; the male spores are converted 
into pollen grains and the antheridia into the fertilizing pollen- 
tubes; the female spores are transformed into embryo-sacs con- 
taining corpuscles within which are the ultimate germ-cells. 
In a certain sense this transition, instead of marking an ad- 
vance in the process of sexual separation, constitutes a step back- 
ward, since the prothallia of Cryptogams, considered as distinct 
individuals, are respectively male and female, while the stamens 
and pistils of the Cycadacee and Conifer, the earliest Phaeno- 
gams developed, though quite distinct in themselves, are both 
borne on the same plant. But the prothallium marks the highest _ 
development reached or possible to the Cryptogam. The Phzeno- 
gam must begin from a point lower down, and in turn evolve sex- 
ually differentiated forms. The distinction of macrospores and 
microspores found only in the Rhizocarpee and Ligulate, and 
which, as already stated, initiated the transition from the Crypto- 
gams to the Phenogams, took place in the same individual, both 
kinds of spores often occurring in the same sporangium, as in 
Salvinia. This, when the two kinds of spores at length came to 
represent the two sexual organs of the Cycad or the Conifer, 
necessarily reunited the sexes once more in the same plant, and 
the process of separation, so well completed-in the higher Crypto- 
