PLANT ORGANS AND ORGANISMS 
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From this we pass to another group in which the bundles form 
three-fourths of a circle and in which the upper bundles show incurv- 
ing orientation, to still another in which as in Nepenthes all of the 
bundles form nearly a cylinder. Finally in Ficus, Geranium, Podo- 
phyllum and other plants showing completely formed cylindric 
petioles, the bundles form a continuous ring enclosing pith and sur- 
rounded by cortex and epidermis as in Dicotyl stems. 
Stipules. — Stipules are lateral leafy or membranous outgrowths 
from the base of the petiole at its junction with the stem. They 
may be divided into two groups, viz.: lateral and axillary. The 
lateral group includes four types, namely, free lateral, lateral adnate, 
lateral connate and lateral interpetiolar. 
Free lateral stipules are seen in Leguminosce, Rosacea, Beeches, 
etc. They are free on either side of the petiole and supplied by 
vascular tissue from the petiolar bundle mass. In appearance and 
duration they may be either green, foliaceous and persistent or mem- 
branous to leathery, scale-like and caducous. Caducous scaly stip- 
ules only function as bud scales through the winter and fall in spring 
as the buds expand. 
Lateral adnate stipules are such as fuse with and are carried up 
with the petiole as wing-like appendages. This type is seen in the 
genus Rosa, in Clovers, etc. 
Lateral connate stipules are such as join and run up with the 
petiole to form a structure which is called a ligule. This structure 
is ‘common to the Graminaceae or Grass family. 
Lateral interpetiolar stipules are common to many species of the 
Rubiaceae. In the genus Cinchona the leaves are opposite and orig- 
inally had free lateral stipules which latter gradually fused with the 
stem, slid across it and adjacent stipules, then fused together to 
form a median structure on either side of the stem. 
The axillary group represent stipules which stand in the axil of 
the leaf with the stem. Such may be free axillary structures, arising 
as distinct processes or connate, when the two stipules unite at their 
margins and sheath the stem, as in many species of the Polygonaceae 
such as Buckwheat, Rhubarb, Yellow Dock, Knot Weeds, etc. The 
sheath formed is called an ochrea. 
Modified Stipules. — In some plants such as the Locust and several 
