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Special Morphology and Classification. 248 
tion of the spores]; while the sporogonia of Musci have 
usually a removable lid or ofercu/um and do not contain 
elaters. 
4. VASCULAR CRYPTOGAMS. These possess true vessels, 
and are also characterised by the development from the 
spore of a leafless pro-embryo of small size, bearing the 
oospheres from which, after fertilisation, the spore-bearing 
plant is produced. ‘The former is, therefore, the sexual, the 
- latter the nonsexual generation. They are classified into two 
series—the J/sosforous and the eterosporous. ‘The former 
produce only one kind of spore ; the pro-embryo, which is. 
developed from this, grows for a considerable time inde- 
pendently of the spore, and bears both the male and female 
organs of reproduction [azthertdia and archegonia|. The — 
Heterosporous Vascular Cryptogams produce, on the con- 
trary, two kinds of spores, larger or macrospores, and. 
smaller or mzcrospores. From the former arise pro-embryos, - 
on which the oospheres are developed; while the latter 
produce only a slight trace of pro-embryo, and almost 
immediately the male elements, the spermatozoids or an- 
therozoids. ‘The Isosporous Vascular Cryptogams are — 
divided into three classes:—1. ices. The pro-embryo 1s 
above-ground and green; the sporangia are epidermal 
structures (trichomes) of the leaves. 2. Hguzsetacee. The 
pro-embryo is above-ground and green; the verticillate 
leaves are provided with sheaths ; the sporangia are formed 
several together on the margin of peltate leaves, which form 
a terminal fructification. 3. Ophioglossacee. The pro- 
embryo is subterranean, not green, and moncecious; the 
stem is unbranched ; the sporangia are formed on a branch 
of the leaf which forms a panicle or spike. The Hetero- 
sporous Vascular Cryptogams include the two remaining 
classes :—4. KRhizocarpee. The sporangia are formed in 
considerable numbers in the interior of hollow capsules, the 
sporocarps, and contain either a single macrospore or a 
number of microspores. 5. Lycopodiacee. The sporangia 
