Azolla.]} SALVINIACES. 1031 
tered on the divisions of an altered submerged leaf, or in pairs in 
the axils of the leaves, globose or ovoid, membranous, indehiscent, 
of two kinds, both borne on the same plant; one kind containing a 
single or many macrosporangia, the other enclosing numerous 
microsporangia. Macrosporangia containing a single macrospore ; 
microsporangia with numerous microspores. 
Genera 2; species about 18, mainly tropical or subtropical. In germina- 
tion the macrospore produces a rather large prothallium, which remains at- 
tached to it, and which bears one or more archegonia. The microspores each 
develop a rudimentary prothallium bearing a single antheridium containing 
spermatozoids, fertilisation taking place in the same way as in ferns. In the 
genus Salvinia, which is not found in New Zealand, the antheridia are formed 
while the microspores are contained within the microsporangium; but in 
Azolla the microspores escape in groups called massule, each with its proper 
membrane, and the antheridia are developed within the massule. 
1. AZOLLA, Linn. 
Floating water-plants. Stems copiously pinnately branched, 
emitting on the under-side numerous rootlets. Leaves densely im- 
bricating, very minute, sessile, deeply and unequally 2-lobed. 
Sporocarps or conceptacles in pairs in the axils of the leaves on 
the under-surface of the stem, of two kinds: one kind larger, glo- 
bose, enclosing numerous microsporangia, each of which contains 
numerous microspores arranged in separate groups or massule 
furnished with a membranous envelope; the other smaller, ovoid, 
containing a single macrosporangium within which is a solitary 
macrospore. Macrospores each crowned with few or many swim- 
ming-floats; massule of the microspores armed with simple or 
hooked bristles. 
A small genus of 4 or 5 species, found in most tropical or warm temperate 
regions. 
1. A. rubra, Ff. Br. Prodr. 167. — Floating, red or reddish- 
green, often gregarious and covering large sheets of water; the 
separate plants 4-1 in. long, orbicular or ovate or somewhat deltoid, 
copiously bipinnate. Leaves densely imbricating, about 54, in. long, 
2-lobed, the lobes ovate, obtuse. Larger sporocarps globose, about 
a5 in. diam.; the massule of the microspores armed with copious 
hooked bristles. Smaller sporocarps hardly more than half the 
size, oblong; the solitary macrospore crowned with 3 swimming- 
floats. — Hook. f. Fl. Nov. Zel. ii. 56; Handb. N.Z. Fl. 392; 
Benth. Fl. Austral. vii. 680; Bak. Fern Allies, 137. 
NortH AND SoutH IsntAnpDs, STEWART Is~LAND: Abundant in still waters 
throughout. 
Also found in Australia and Tasmania, and very closely allied to the South 
American 4d. filicwloides, Lam., of which some authors consider it to be a 
variety. 
