SPERMATOPHYTES 181 
A. GYMNOSPERMS 
This group includes the primitive seed plants, and to understand their 
relation to pteridophytes it will be necessary to consider them in their 
historical sequence. Seven great groups are recognized: (i) Cycado- 
Jilicales, (2) Bennettitales, (3) Cycadales, (4) Cordaitales, (5) Ginkgoales, 
(6) Coniferales, and (7) Gnetales. The first, second, and fourth of these 
groups are extinct. 
(i) CYCADOFILICALES 
Discovery. The discovery of the existence of this most primitive 
group of seed plants, known only in the Paleozoic and chiefly in the 
Carboniferous, is so recent that a brief outline will be of interest. The 
Coal-measure deposits are notable for the remains of fernlike plants, 
and such plants constitute about one half of the known vegetation of the 
time. Until recently all of these plants were thought to be ferns, the 
evidence from their leaf forms and venation appearing to be conclusive. 
Most of them show no sporangia, and such sporangia as do appear are 
mostly of the Marattia type. The first expressed doubt (1883) that these 
fernlike plants were all ferns arose from the persistent absence of spo- 
rangia. Later the anatomy of the stems of several forms was discovered 
to show characters combining those of ferns and of cycads, and for such 
forms the group name Cycadofilices was proposed (1899). In 1903 
seeds were found on the leaves of certain of these Cycadofilices, and the 
group name Pteridospqrms was proposed to include the Cycadofilices 
that bear seeds. Finally, in 1905 the microsporangia were discovered; 
and curiously enough some of these microsporangia were the sporangia 
of so-called ferns. Therefore, a knowledge of the existence of ferns dur- 
ing the Carboniferous came to depend more upon inference than upon 
any sure recognition of their remains. In any event, it seems certain 
that almost all of the so-called fern vegetation of the Carboniferous be- 
longs to these primitive seed plants. The oldest name for the group is 
here adopted, its termination being adapted to that of the other groups 
with which it is coordinate. 
Sporophyte. The habit of the sporophyte body is conspicuously 
fernlike, including not merely the usual fern habit, but also climbers and 
trees. The vascular anatomy, which first separated the group from 
ferns, deserves brief fnention. Three of the four conspicuous types of 
vascular cylinder found among ferns (see p. 156) are found in the stems 
of Cycadofilicales, the three representative genera illustrating them be- 
