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PinkMonkey Online Study Guide-Biology

(A) Habit (B) Coralloid roots (C) Green leaf (D) Young Green leaf

Figure 15.8 Cycas


Cycas has dimorphic leaves, (i.e., two types of leaves): scale leaves and green leaves. Both develop spirally around the stem apex. The spirals of scale leaves alternate with those of green leaves. The scale leaves are small and non-green. The green photosynthetic leaves are between 1-3 meters long and unipinnately compound (Fig. 15.8 C and D). They form a crown around the stem apex. Young leaves show circinnate venation (similar to ferns). Each green leaf has a strong petiole and a main rachis with two rows of numerous leaflets (pinnae). Each pinna is long, linear and lanceolate with an entire margin. It has a distinct midrib but lateral veins are absent. Some of the basal leaflets are reduced to spines.

 

Table of Contents

15.0 - Introduction
15.1 Pteridophyta : General Account
15.2 Gymnosperms
15.3 Angiosperms : Dicotyledons
15.4 Angiosperms : Monocotyledons
15.5 Vascularization
15.6 Development of seed habit
15.7 Development of Flower and Fruit

Chapter 16





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