IOWA ACADEMY OF SCIENCE 
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Order II. 
Chaetophorales. 
KEY TO THE FAMILIES. 
A. Filaments simple. 
1. Chloroplast single, parietal with one or more pyrenoids. Sexual repro- 
duction isogamous III. Ulotrichaceae 
2. Cells with thick lamellose coats, usually arranged in a single series within 
a lamellose gelatinous sheath. Sexual reproduction heterogamous ; 
plants monoecious; oogonia with one non-mo tile oosphere; fertilization 
within the oogonium IV. Cylindrocapsaceae 
B. Filaments branched. 
1. With trichomes, or hairs on some part. 
a. Trichomes not terminal. 
* Filaments creeping, trichomes on most of the cells, often swollen at 
the base, epiphytic on submerged plants. Sexual reproduction hetero- 
gamous, plants monoecious, oospheres motile, fertilization taking place 
outside the oogonium II. Herposteiraceae 
** Filaments forming flat expansions or pulvinate branched masses, 
epiphytic on the stems and leaves of submerged plants. Sexual re- 
production heterogamous; plants monoecious or dioecious; oogonia 
with a trichogyne and one non-motile oosphere; fertilization within 
the oogonium and resulting in the formations of a cortical layer on 
the outer surface of the oogonium. Some of the cells of the thallus 
are furnished with fine bristles with basal sheaths . I. Coleochaetaceae 
b. Trichomes terminal, branches attenuated into multicellular hair-like 
prolongations. Chloroplast single, parietal, with one or many pyrenoids. 
All the cells except those of the rhizoids and hairs are capable of pro- 
ducing zoogonidia or gametes. Sexual reproduction isogamous 
V. Chaetophoraceae 
2. Without trichomes. 
a. Chloroplast single, parietal, with or without a single pyrenoid. 
Branches scarcely attenuated. Zoogonidia and gametes produced in spe- 
cial cells. Sexual reproduction isogamous VI. Microthamniaceae 
b. Chloroplasts several, parietal, without pyrenoids. Zoogonidia and 
gametes produced in special gonidangia. Sexual reproduction isogamous. 
Thallus branched, terrestrial or arboreal VII. Trentepholiaceae 
1. Coleochaete. 
Family I. 
Coleochaetaceae. 
KEY TO THE SPECIES. 
Filaments not closely united into a membrane C. soluta 
Filaments closely united into a membrane. 
Thallus not circular C. scutata 
Thallus circular C. orbicularis 
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