. Lessons in botany. Botany. SEEDS AND SEEDLINGS. 209 envelope grows up around the seed; an example of this is found in the case of the red berries of the '' yew '' (taxus), the red outer coat being an extra growth, called an aril. In the willow and the milkweed an aril is developed in the form of a tu'ft of hairs. (In the willow it is an outgrowth of the funicle, = stalk of the ovule, and is called a funicular aril ; while in the milkweed it is an outgrowth of the micropyle, = the open end of the ovule, and is called a micropylar aril.) 343. Increase in size during seed formation.—Accompany-
. Lessons in botany. Botany. SEEDS AND SEEDLINGS. 209 envelope grows up around the seed; an example of this is found in the case of the red berries of the '' yew '' (taxus), the red outer coat being an extra growth, called an aril. In the willow and the milkweed an aril is developed in the form of a tu'ft of hairs. (In the willow it is an outgrowth of the funicle, = stalk of the ovule, and is called a funicular aril ; while in the milkweed it is an outgrowth of the micropyle, = the open end of the ovule, and is called a micropylar aril.) 343. Increase in size during seed formation.—Accompany- ing this extra growth of the different parts of the ovule in the formation of the seed is an increase in the size, so that the seed is often much greater in size than the ovule at the time of fer- tilization. At the same time parts of the ovary, and in many plants, the adherent parts of the floral envelopes, as in the apple; or of the receptacle, as in the strawberry; or in the involucre, as in the acorn; are also stimulated to additional growth, and assist in making the fruit. In the pine not only the ovular coat grows to form the outer coat of the seed, the entire '' scale'' increases greatly in size, and when the fruit is mature, a portion of this scale splits off forming a " wing " to the seed (see fig. 169). 344. Endosperm in the ripe seed.—In many seeds when they are ripe there is still a large amount of the endosperm surround- ing the embryo (albuminous seeds). This is the case in the violet, as shown in fig. 186. Other examples of this kind are found in the butter- cup family, the grasses, the lily, palm, jack-in-the-pulpit, etc. When the seed germinates this endosperm is used as food by the embryo. 345. Endosperm absent in the Seed of violet, external view, and section. The section shows the em- ripe Seed. In many Other plants bryo lying in the endosperm. all of the endosperm is consumed by the embryo during its giqjrth in the formation of the seed. T
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