Text-book of botany, morphological and physiological . results from itsabsorption by the rapid growth of the embryo before the ripening of the seed;only in a very few cases is it rudimentary from the first (Tropieolum, Trapa). InNymphaeaceae and Piperaceae the embryo and the endosperm which surroundsit both remain small, the rest of the space within the testa being occupied byperisperm. The Embryo generally attains but very small dimensions in the small-seededparasites and saprophytes destitute of chlorophyll, and remains without differentiationuntil the time of ripening of the seed; in Monotr
Text-book of botany, morphological and physiological . results from itsabsorption by the rapid growth of the embryo before the ripening of the seed;only in a very few cases is it rudimentary from the first (Tropieolum, Trapa). InNymphaeaceae and Piperaceae the embryo and the endosperm which surroundsit both remain small, the rest of the space within the testa being occupied byperisperm. The Embryo generally attains but very small dimensions in the small-seededparasites and saprophytes destitute of chlorophyll, and remains without differentiationuntil the time of ripening of the seed; in Monotropa it never consists of more thantwo cells, and even in Pyrola secunda, which possesses chlorophyll, only of from eightto sixteen (Hofmeister). The ripe seeds of Orobanche, Balanophora, Rafflesiacea^,&c., contain a very small undifferentiated embryo in the form of a roundish mass oftissue; the embryo of Cuscuta is of moderate size and length, but the formation ofleaves and roots on the filiform stem^ is suppressed. The mistletoe (Loranthaceee),. I-ir,. \o\—Chivio}ianthus/ra):ians: A liorizontal section of the nearly ripe fruit: B longitudinal section of tliin pericaqi. e of the endosperm, c cotyledons; C the embryo removed from the seed, showingthe cotyledons rolled round one .nnother, the radicular end below. on the other hand, parasitic but containing chlorophyll, produces an embryo whichis not only large but well-developed. If the embryo of the ripe seed is differentiated, as is generally the case, itconsists of an axis and two primary opposite leaves (cotyledons) betvv^een which theaxis terminates as a naked vegetative cone (Cucurbita), or bears a bud which sometimesconsists of several leaves ( Vicia Faba, Fig. 405, Phaseolus, Quercus, &c.). Insteadof the two opposite cotyledons, a whorl of three is not unfrequently formed in thoseplants which normally possess only two (Phaseolus, Amygdalus, Quercus, &c.).The opposite cotyledons are usually ali
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
