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KEY TO THE FAMILIES Lm^A^r 



EMBRYOPHYTA SIPHONOGAMA 



(PHANEROGAMAE) 



1. Ovules naked, borne on a floral axis without carpels, or on open carpels 



without a stigma. Perianth simple or none. Flowers unisexual. Stem 



woody. [Subdivision GYMNOSPERMAE.] 2 



Ovules encased in the ovary formed by stigma-bearing carpels and nearly 

 always closed to the top, rarely (Resedaceae) open above. [Subdivision 

 ANGIOSPERMAE] 5 



2. Leaves pinnately compound or dissected, forming a crown at the top of the 



stem. Stem simple or scantily branched towards the top. Juice muci- 

 laginous. Perianth none. Stamens with numerous pollen-sacs. Embryo 

 with 2 more or less connate cotyledons. [Class CYCADALES.] 



1. Cycadaceae. 



Leaves undivided, scattered along the branches of the stem, rarely {Gneta- 



ceae) leaves 2, arising from the top of an undivided turnip-shaped stem 



and sometimes splitting lengthwise. Stamens with i — 9 pollen-sacs. 



Embryo with 2 — 15 free cotyledons 3 



3. Perianth present. Juice not resinous. Leaves not needle-shaped. Shrubs. 



[Class GNETALES.] 4. Gnetaceae. 



Perianth absent. Juice resinous, rarely scarcely so, but then leaves needle- 

 shaped. Leaves needle- or scale-shaped. [Class CONIFERAE.] . 4 



4. Seeds overtopping the fleshy or rudimentary carpels and surrounded by a 



fleshy aril. Carpels with i ovule 2. Taxaceae. 



Seeds concealed between the carpels, without an aril. Carpels usually with 

 2 or more ovules 3. Pinaceae. 



5. (i.) Embryo with a single cotyledon, rarely undivided. Vascular bundles 



scattered in the stem. Leaves usually parallel-veined (net- veined in 

 many Araceae Dioscoreaceae and Taccaceae and a few Hydrocharitaceae 

 Liliaceae and Orchidaceae), generally narrow entire and sessile with a 

 dilated base. Flowers usually 3-merous. [Class MONOCOTYLEDO- 



NEAE.] 6 



Embryo with 2 cotyledons, rarely with only one well-developed cotyledon 

 or undivided. Vascular bundles of the stem nearly always disposed in 

 a cylinder. Leaves usually net-veined, rarely sessile with a dilated base 

 and a narrow entire blade. Flowers usually 4- or 5-merous. [Class 

 DICOTYLEDONEAE.] 5« 



A 



