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15
INTRODUCTION

fused into one, and are then called the keel (fig. 85, a, b, c).

In the Labiatæ there are five petals fused together into an upper and lower lip, the upper lip being bifid and formed of two petals, and the lower trifid, formed of three. In the Snap-dragon, the tube of the corolla is closed by a curve of the lower lip.

At the base of many flowers we find a gland secreting honey, and called the nectary.

Arrangement of Flowers

Flowers are called simple or compound according to whether one or more rise from a common stalk.

Simple flowers may be either (a) terminal, when they rise at the end of a stalk (as in the Snowdrop); or (b) lateral, when they are placed in the axil of a leaf.

Compound flowers have received various names according to the manner in which they are arranged. Among the more important of these are the spike, the raceme, the panicle, the umbel, the cyme, and the head.

A Spike has a long axis, and sessile or very shortly stalked flowers (fig. 86). A spike of corn is called an ear.

A Cob (of Maize) is a spike with a thickened axis; a catkin is a spike with unisexual flowers (as