ดา ระ เอ ย ก اپ‎ 95 
Ferns. In the Isoetes (a Lycopod) we see, for the first time 
in our brief survey of the vegetal kingdom, a stem present- 
ing woody layers one inside of the other, one of the distin- 
guishing features of trees like the Oak, Walnut, Chestnut, 
Pine, Fir, Cycas. This fact is an important one, as will 
appear later. The reproduction of the Lycopodiacez and 
Rhizocarpe differs from that of any plants of which we 
have yet spoken. There are found in the Lycopodiacee 
both large and small spore-cases, of which the former 
(Fig. 128) contain only four large spores, the latter (Fig. 
128) many small ones. In Selaginella the leaves are spike- 
shaped, and at the base of the leaf is found either a large 
or small spore-case. Each spore of the large spore- 
case may produce within its cavity a Prothallus like that 
of the Fern; but it will be remembered that the Prothallus 
of the Fern is produced outside of the spore, whereas the 
Prothallus ofthe Lycopod is developed inside the large 
spore. In the Prothallus of the Lycopod, Archegonia, with 
their embryo-cells, alone are found; the Antheridia, with 
their spiral filaments, coming only from the small spores. 
Finally the large spore bursts, freeing its Prothallus. The 
spiral filament of the Antheridium of the small spore, 
coming in contact with the embryo-cell in the Archegonium 
in the Prothallus of the large spore, gives rise to the new 
Lycopod, which, in Selaginella, is a little stem supporting 
two leaves, one on each side. (Fig. 129.) This kind of 
reproduction is seen in the Rhizocarpe. By comparing 
the reproduction noticed in the Fern, Horse-tail, Rhizocarp, 
and Lycopod, the following series becomes apparent: the 
Ferns and Horse-tails produce one kind of spore; from 
this spore is developed a Prothallus containing both Arche- 
gonia with their embryo-cells, and Antheridia with their 
Spiral filaments. The Rhizocarpe and Lycopodiacex 
produce two kinds of spores, large and small; in the 
Pillvort and Pepperwort the large and small spores are 
