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1878. ] On the Genealogy of Plants. 369 
the few genera which have been grouped under this order vary 
enormously in everything but their mode of inflorescence. 
Whether they have been developed independently from the 
Cryptogams or have been off-shoots from lower Gymnosperms 
must therefore remain one of the problems of botanical science; 
but it is a problem, as we shall presently see, which derives its 
great importance from the special 7é/e which the Gnetacee have 
been made to play, as a connecting link between the Gymno- 
sperms and the Dicotyledons. 
The highest marks of organization in the vegetable kingdom 
are the exogenous structure and the encasement of the germ. 
These may be regarded as the two great ends towards which 
vegetal life is perpetually striving. One of these ends is attained 
by the Monocotyle or endogenous Angiosperms; both of them 
have been secured in the Dicotyle or exogenous Angiosperms. 
Although most of the intermediate stages, from the naked- 
seeded Cycad to the closed ovary of the Monocotyledon, have 
been obliterated, or have not been discovered, the evidence is 
nevertheless abundant that such a transition has taken place. If 
we consider what may be called their phystognomy alone, the 
descent of the true palm from the sago-palm, or both from a 
common ancestor in the Cycadacee would seem in a high degree 
probable. The great divergence in the matter of floral envelopes 
may be accounted for on the supposition that the differentiation, 
as is known to be frequently the case, was chiefly confined to the 
reproductive system and only slightly affected other characters. 
The absence of intermediate stages in our existing flora could 
then be explained by the now well understood law of the ephe- 
meral nature of transition forms. In fact the Cycad is itself a 
transition form connecting the Cryptogams with the true flowering 
plants, or Angiosperms, and as such it is doubtless a compara- 
tively ephemeral state. So far as general aspect or physiognomy 
is concerned, the ordinary observer, without trained scientific 
insight, naturally and instinctively classes the palm, the sago- 
palm, and the tree-fern in one and the same group, little imagining 
that botanists class them each in such a widely different group, — 
Language itself builds on so obvious a resemblance. What we 
call the sago-palm, connecting it with the higher type, the Ger- 
mans call the palm-fern (Pa/m/farn), connecting it with both the 
higher and the lower types of vegetation. Should further study- 
>: ME E, 
