31A

Citrus aurantium (orange) Aurantiaceæ.

The cotyledons are hypogean. After the plumule has grown to about an inch in length, the two cotyledons may often be found beneath the earth separated by as much as nearly 1/5 of an inch, owing to the growth of the stem between the bases of the two petioles. The upper cotyledon is very thin is sometimes only about half as long as the other, or even relatively much shorter, so This f that it is evidently tending towards abortion.

This fact is worth notice, as some few plants, for instance Ranunculus ficaria & Cyclamen Persica produce only a single cotyledon. The circumnutation of the plumule of an orange which at the close of the observations was .59 of an inch (15 m.m) in height above the ground, is shown in the annexed figure, as observed during a period of 44° 40'.