SEED-BEARING PLANTS 409 
angiosperm means "enclosed seed." 1 The fundamental 
distinction between gymnospermy and angiospermy was 
first made clear by one of the greatest of English bota- 
nists, Robert Brown, in 1827 (Fig. 10). 
363. Comparison with Ferns. The cycads resemble the 
true ferns in several points in the vernation of their 
leaves (coiled in the bud), in the venation of the leaves 
(forked veins), in the possession of sori (for microspor- 
angia), in having multiciliate sperms, in having sporo- 
phylls (megasporophylls) that closely resemble foliage 
leaves, and in having the embryo dependent at first upon 
the prothallus for nourishment, but later becoming 
established as an independent plant. 
They differ from ferns in having the non-green gameto- 
phyte dependent for nourishment throughout its life 
upon the tissues of the sporophyte. In the heterosporous 
habit they differ from the true ferns, but resemble the 
higher fern relatives, like Selaginella. Their greatest 
step forward is the development of a seed. They are the first 
true seed-bearing plants to be met with among living 
species, as we ascend from the Algae. How closely 
Selaginella approaches the formation of a true seed may 
be seen by referring to the condition in the megaspor- 
angium following fertilization (Fig. 284). // the female 
gametophyte of Selaginella should remain within the walls 
of the megaspore; if the embryo should undergo a period of 
rest after the formation of the young stem and first leaves, 
and if this entire structure should remain within the mega- 
sporangium, we should have a true seed in Selaginella. 
The cycad seed is primitive (or imperfect as a seed), 
1 From the Greek, angeion (d-yyeioi'), a vessel + sperma (trirkpfta), 
seed. 
