CHAPTER XXIII 
CHARACTERISTICS OF SPORE-PLANTS 
262. Definition of a Spore-Plant.— A spore-plant is one 
which does not form seeds but is reproduced by means of 
a one-celled reproductive body called a spore! Such bodies 
do not contain an embryo; they are of microscopic size and 
in all ways are far simpler than seeds. 
263. Diversity among Spore-Plants. —Spore-plants are 
extremely diverse in their size, structure, and life habits, 
and in the details of their reproductive processes. 
The simplest and smallest among them are one-celled 
organisms, not more than a fifty-thousandth of an inch in 
diameter, while the largest seaweeds are nearly or quite a 
thousand feet in length, and tree ferns reach a height of 
thirty or forty feet, with ample spreading crowns (Plate XI). 
The pale or colorless spore-plants, such as bacteria, 
molds, and toadstools or mushrooms (Figs. 169, 172, 185), 
can live only as parasites, taking their food from living 
animals or plants, or as saprophytes, feeding on the prod- 
ucts of decay. 
The green spore-plants, however, carry on their nutritive 
processes as the higher plants do (Chapter x11), and in 
all such relatively complex forms as the horsetails and 
‘1 Seed-plants (commonly called flowering plants) also produce spores (Sect. 
383), but those forms which are treated in Chapters XXIII-XXVII may fairly 
be called spore-plants since the spore is their highest means of reproduction. 
211 
