Text-book of botany, morphological and physiological . g. 44, p. 43. Not unfrequently a luxuriant growth of the parenchyma takes place beneath thehair; and this is imitated also by the epidermis; the hair itself is then borne on a peg-shaped prominence or protuberance of the leaf or stem, and is often deeply implantedinto it in its lower part; as, for instance, in the prickles (stinging hairs) of the stinging-nettle. Thus also the prickles (climbing hairs) on the six projecting angles of thestem of the hop grow into a large basal protuberant mass of tissue, while the hair-cellgrows in opposite
Text-book of botany, morphological and physiological . g. 44, p. 43. Not unfrequently a luxuriant growth of the parenchyma takes place beneath thehair; and this is imitated also by the epidermis; the hair itself is then borne on a peg-shaped prominence or protuberance of the leaf or stem, and is often deeply implantedinto it in its lower part; as, for instance, in the prickles (stinging hairs) of the stinging-nettle. Thus also the prickles (climbing hairs) on the six projecting angles of thestem of the hop grow into a large basal protuberant mass of tissue, while the hair-cellgrows in opposite directions into two sharp points. Such double-pointed unicellularhairs occur also on the under-side of the leaf of Malpighia urens; they are 5-6 mm. long,fusiform, very thick-walled, and grow into the epidermis by their central part (withoutprotuberance). In this case they easily become detached, and remain sticking in the H6 MORPHOLOGY OF TISSUES. skin of the hand which touches the leaf. (For further details on the Morphology ofHairs cf. sect. 22.). Fig. 72.—Development of the hairs on the calyx of a flower-bud oi Althu-a rosea (X300); A wh woolly-hairs of the innerside; b and c glandular hairs in different stages of development; at a (to the right) rudiment of a glandular hair;ep always signifies the (still young) epidermis. The figures a. A,^ (to the left) and y (to the right below) show the firststages of development of the stellate hairs (or rather tufts of hairs), the subsequent condition of which may be comparedin Fig. 44 (p. 43); at ^ a is the hair in longitudinal section ; /3 and y show the appearance seen from above; the cellsare rich in protoplasm ; the formation of vacuoli (->) in the protoplasm is beginning in y. T:he Stomata^ are always absent from the epidermis of true roots; on the otherhand they are usually present on underground axial organs and leaves; even on sub-merged parts they are occasionally found (Borodin, /. c.); but they are formed in thelarge
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
