CRYPTOGAMS 357 
The analogies between the sequence of alternations in the 
two classes will be made clearer by a comparison of the 
accompanying diagrams. The corresponding terms applied 
to the various organs stand in the same vertical row. Dia- 
gram (1) shows the process as it takes place in the more 
highly developed Pteridophytes; diagram (2) the corre- 
sponding phases in angiosperms. 
PTERIDOPHYTES 
; mospl—> mic—> mo—> anG—> ant —> mg 
(A) s » 608 ——> S 
Mospl—-> Mgc—> Mo—+> arG ——> are —~> fg —> 
mospl, microsporophyll; mic, microsporangium; mo, microspores; anG, male 
gametophyte; ant, antheridia; mg, antherozoids. The letters in the lower line 
stand for the corresponding female organs. 
SPERMATOPHYTES 
not——> ge — 
st si ae fe developed ‘ x 
(2) S 00S——>S) 
oe developed fs 
P ou em: g only in re 
gymno 
sperms 
st, stamen; an, anther; pol, pollen; fc, food cells in pollen grain; ge, generative 
cell ; p, pistil ; ov, ovules; em, embryo sac; end, endosperm ; ec, egg cell. 
415. Disappearance of the gametophyte. — The seed is a 
comparatively recent development in plant evolution. It 
has no counterpart anywhere among the cryptogams, but is 
strictly characteristic of the three great orders of Spermo- 
phytes: Monocotyl, Dicotyl, and Gymnosperms, which 
compose the greater part of the vegetation of the globe. 
Structurally, it is a matured sporangium containing a rudi- 
mentary sporophyte (the embryo), and a reduced gameto- 
phyte (the embryo sac), which, under the form of endosperm, 
has dwindled to an insignificance that makes it difficult to 
recognize it as a phase in an alternation of generations. 
416. Significance of the sporophyte. — The gametophyte 
is obviously a more ancient and primitive structure than the 
sporophyte, which first becomes prominent in the ferns and 
