GENERAL KEY TO THE ORDERS. 



PAGB 



Subkingdom PTERIDOPHYTA i 



Spores developing into flat or irregular prothallia which bear the repro- 

 ductive organs (antheridia and archegonia); flowers and seeds none. 



Sporanges (spore-cases) borne on the back of a leaf, or in spikes or panicles. 



Order i. FILICALES i 



Sporanges contained in sporocarps. Order 2. SALVINIALES. . . 19 



Sporanges clustered underneath the scales of a terminal cone-like spike; stems 



jointed, rush-like. Order 3. EQUISETALES. . . 21 



Sporanges borne in the axils of scale-like or tubular leaves. 



Order^ LYCOPODIALES.. 23 



Subkingdom SPERMATOPHYTA 30 



Microspores (pollen-grains) developing into a tubular prothallium (pollen- 

 tube); macrospores (embryo- sac) developing into a minute prothallium, and, 

 together with it, remaining enclosed in the macrosporange (ovule) which 

 ripens into a seed; flowering plants. 



1. Ovules not enclosed in an ovary. Class i. GYMNOSPERMAE. 30 



2. Ovules enclosed in an ovary. Class 2. ANGIOSPERMAE... 38 



* Embryo with i cotyledon ; stem with no distinction into pith, wood and 

 bark ; leaves mostly parallel- veined. Subclass i. MONOCOTYLEDONES. . 38 



f CARPELS i OR MORE DISTINCT (united, at least partially in family Scheuch- 

 zeriaceae of the order Naiadales. in which they are mostly united until matu- 

 rity, and in family Vallisneriaceae, also of the Naiadales, which are aquatic 

 herbs with imperfect flowers); parts of the flowers mostly unequal in number. 



Inflorescence various, not a true spadix. 



Flowers not in the axils of dry chaffy scales ; our species aquatic or marsh 

 plants. 



Endosperm mealy or fleshy ; perianth of bristles or chaffy scales; flowers 



monoecious, spicate or capitate. Order i. PANDANALES. . . 38 



Endosperm none, or very little ; perianth corolla-like or herbaceous, or 



none. Order 2. NAIADALES 40 



Flowers in the axils of dry chaffy scales, arranged in spikes or spikelets. 



Orders. GRAMINALES. . 61 



Inflorescence a fleshy spadix, with or without a spathe; or plants minute, floating 

 free, the flowers few or solitary on the margin or back of the thallus. 



Order 6. ARALES 228 



ff CARPELS UNITED INTO A COMPOUND OVARY ; parts of the usually com- 

 plete flowers mostly in 3's or 6's. 



Seeds with endosperm. 



Flowers regular, or nearly so (corolla irregular in Commelina). 



Endosperm mealy; ovary superior. Order 7. XYRIDALES.. . . 235 



Endosperm fleshy or horny; ovary superior or inferior. 



Order 8. LILIALF.S 244 



Flowers very irregular; ovary inferior. Order 9. SCITAMINALES. 288 



Seeds without endosperm, very numerous and minute; ovary inferior. 



Order 10. ORCHIDALES.. 288 



vii 



