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FOC | Family List | FOC Vol. 4 | Cycadaceae

1. Cycas Linnaeus, Sp. Pl. 2: 1188. 1753.

苏铁属 su tie shu

Epicycas de Laubenfels.

Morphological characters and geographical distribution are the same as those for the family.

The angle of insertion of the leaflets to the rachis is that formed between the leaflet and the longitudinal axis of the rachis. Features of leaflets in 1-pinnate leaved species refer to those of the middle part of the leaf blade.

1 Leaves 2- or 3-pinnate; leaflets dichotomously forked.   (2)
+ Leaves 1-pinnate; leaflets simple.   (4)
2 (1) Leaves 2-pinnate; leaflets dichotomously 1(-3)-forked into linear, often irregular segments (ultimate leaflets), each 10-38 cm with apex attenuate to long acuminate   3 Cycas micholitzii
+ Leaves 3-pinnate; secondary leaflets dichotomously (2 or)3-5-forked into linear, regular segments.   (3)
3 (2) Leaves 1(or 2), to 7 m; segments obovate-linear, apex shortly acuminate to caudate; sterile blade of megasporophylls with 25-35 subulate lobes   1 Cycas multipinnata
+ Leaves (3-)5-11(-15), to 2.7 m; segments linear, apex long attenuate or long acuminate; sterile blade of megasporophylls with 39-51 filiform lobes   2 Cycas debaoensis
4 (1) Leaves strongly V-shaped in cross section, longitudinally recurved; margin of leaflets revolute (slightly recurved in C. taitungensis).   (5)
+ Leaves flat to inconspicuously V-shaped in cross section, longitudinally flat; margin of leaflets not revolute (except in C. ferruginea).   (7)
5 (4) Trunk not tomentose at apex; bark pale gray, smooth toward base of trunk; mature leaflets glaucous   15 Cycas hongheensis
+ Trunk densely tomentose at apex; bark black, scaly; mature leaflets not glaucous.   (6)
6 (5) Leaflets strongly recurved along margin; sterile blade of megasporophylls ovate to narrowly so, deeply laciniate; sclerotesta of seed not grooved on sides   6 Cycas revoluta
+ Leaflets flat or slightly recurved along margin; sterile blade of megasporophyll suborbicular or rhombic-orbicular, pectinate; sclerotesta of seed with 2 or 3 irregular grooves on each side   7 Cycas taitungensis
7 (4) Trunk subterranean, base not swollen; median leaflets (12-)18-25 mm wide, margin often undulate; median microsporophylls blunt.   (8)
+ Trunk not subterranean (or, if so, then base swollen); median leaflets 6-11(-14) mm wide, margin flat (revolute in C. ferruginea); median microsporophylls spinose.   (9)
8 (7) Petioles green in 1st year; megasporophylls 5-15(-20), loosely grouped, sterile blade divided into 15-25 lobes   4 Cycas balansae
+ Petioles blue in 1st year, later green; megasporophylls 25-50, densely grouped, divided into 33-45 lobes   5 Cycas segmentifida
9 (7) Leaves (0.7-)1-3 m × 30-60 cm; terminal lobe of sterile blade of megasporophyll usually flattened.   (10)
+ Leaves 0.5-1(-1.3) m × (12-)20-30(-40) cm; terminal lobe of sterile blade of megasporophyll subulate, not flattened.   (12)
10 (9) Trunk inflated; bark white-gray, nearly smooth toward base of trunk; median leaflets often less than 10 mm wide; petiole densely spinose from base upward; seeds 3.5-4.5 cm   9 Cycas hainanensis
+ Trunk cylindric; bark dark, scaly; median leaflets often more than 11 mm wide; petiole without spines or with sparse spines near base; seeds 2.5-3 cm.   (11)
11 (10) Leaflets longitudinally inserted at 55-75° to rachis; apex of cataphylls with hard point; sterile blade of megasporophyll rhombic-ovate; sclerotesta of seed finely verrucose   10 Cycas taiwaniana
+ Leaflets longitudinally inserted at ca. 50° to rachis; apex of cataphylls with soft point; sterile blade of megasporophyll broadly ovate, obovate, or suborbicular; sclerotesta of seed smooth   11 Cycas szechuanensis
12 (9) Trunk cylindric, 1-7 m; bark white-gray, gray, or brown, scaly or raised; pollen cones (25-)30-45 × 8-15 cm, microsporophylls 3.5-6 cm; megasporophylls 13-20 cm.   (13)
+ Trunk subterranean, base swollen; bark gray, smooth; pollen cones 20-30 × 6-8 cm, microsporophylls 1.5-3 cm; megasporophylls 8-14 cm.   (14)
13 (12) Trunk often dichotomously branched toward apex, to 16 m, apex not tomentose; bark gray or white-gray, smooth toward base of trunk; leaflets with midvein sulcate adaxially and margin revolute to slightly recurved; seeds 4.5-6 × 4-4.7 cm   16 Cycas pectinata
+ Trunk simple, to 2(-3) m, apex densely tomentose; bark brown to dark gray, scaly; leaflets with midvein never sulcate adaxially and margin flat to slightly recurved; seeds 2.5-3.5 × 2.2-3 cm   8 Cycas panzhihuaensis
14 (12) Leaflets longitudinally inserted at 55-65° to rachis; petiole with 9-16 spines along each side throughout length (SW Hainan)   14 Cycas changjiangensis
+ Leaflets longitudinally inserted at ca. 90° to rachis; petiole with 0-8(or more) spines along each side often only in apical part (W Guangxi).   (15)
15 (14) Young leaves densely rusty brown tomentose abaxially; leaflets not overlapping, light green at maturity, 20-30 cm × 5-12 mm, base attenuate, margin strongly revolute   12 Cycas ferruginea
+ Young leaves sparsely red-brown tomentose abaxially; leaflets often overlapping, dark green at maturity, 10-18 cm × 14-18 mm, base usually truncate, margin flat or only slightly revolute   13 Cycas miquelii

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