i 
229, Structural and Physiological Botany. a 
of sporangia (Fig. 450 B, IL, Ill.): macrosporangia, in 
which are formed four large macrospores ; and microsporangia, 
in which a greater number of much smaller spores, the mz- 
crospores, are developed. The microspores are the an- — 
theridia, and break up into a small number of cells, one 
of which remains unproductive and may be regarded as 
an abortive pro-embryo, while antherozoids are developed 
in the remainder. The macrospores, on the other hand, as 
in the Rhizocarpez, produce a transitory pro-embryo or pro- 
thallium, which bears archegonia opening outwardly (Fig. | 
450 B, Iv.), and in their interior a central cell with its oosphere. 
In the Isoeteze the pro-embryo entirely fills up the macro- 
spore ; while in the Selaginellez it is attached to its apex 
as a cap-shaped appendage. After fertilisation, which pro- 
cess has not yet been directly observed, the embryo is, in 
Lsoétes, developed directly from the oosphere, while, in Se/a- 
ginella, the latter forms at first a filiform sasfensor, on which 
the young plant is then developed. The mode of reproduc- 
tion of the Lycopodiez is still unknown, and at present 
_ only one kind of spore has been observed in them, corre- 
sponding in its external characters to the microspores of the 
other families. It is obvious that there is in the Lycopodi- 
aceze an alternation of generaticns resembling that which 
prevails in other Vascular Cryptogams. ‘They are also pro- 
pagated in a non-sexual vegetative manner by means of 
gemme, that is, by buds formed in the axils of the leaves, 
which becomé detached from the parent-plant and develope 
into new individuals. 
[The Lycopodiacez are divided into three families, as under : 
1. Lycopodiee. ‘Terrestrial plants with small leaves all of one size ; 
only one kind of spore known: Lycopodium, Tmesipterts, Phylloglossum, 
Psilotum. , 
2. Selaginellee. Terrestrial plants with small leaves of two differ- — 
ent sizes ; two kinds of spores: Selagenella. 
3. Lsoétee. Aquatic plants with long grass-like leaves ; two kinds 
of spores : Lsoétes. | 
The number of species is about three hundred ; all comparatively 
