73 



ADHESION. 



ADIPOSE TISSUE. 



Guided by these facts, modem botanists have made use of this 

 property of adhesion to explain the nature of every organ that plants 

 bear, and there are few anomalies that are not due iu a great measure 

 to the union of contiguous parts. 



Some leaves are said to be stem-clasping, or amplexicaul, when their 

 base partially surrounds the stem (fig. a); while some stems are said to 

 be perfoliate, when they seem as if they pierced through the leaf, as 

 in Bupleurum rotundifoliuin (fig. 6); but the latter differ from the 

 former only in this, that in the first the lobes at the base of the 

 leaf embrace the stem without adhering, while in the second they not 

 only clasp the stem but grow together where their margins come in 

 contact. Some leaves are hollow, as in the Pitcher Plant, and these 

 were formerly thought to be special organs with which no analogy 

 could be discovered ; they are now known to be leaves which have 

 rolled up so that then- opposite margins come in contact and adhere. 

 Other leaves, growing from opposite sides of a stem, adhere in conse- 

 quence of their basea becoming connate (fiy. c), as in the honeysuckle ; 

 and finally there are others, many of which grow in what botanists 

 call a whorl, that is to say, all round a stem upon the same plane, and 

 adhere by their margins into a sheath (fiy. d), as in Casuarina. 



Adhesion. 



In other organs adhesions of a similar nature occur. 



In the calyx, all the sepals, or parts, are often distinct, as in the 

 Kanuncului ; but they also often adhere by their edges, into a sort 

 of cup, aa in the cherry. In the corolla the petals are either all 

 separate, an in the rose, or they adhere by their edges into a cup or 

 bell, an in the different heaths, Campanula, and the like. 



Similar adhesions take place between the stamens. In the rose they 

 are all distinct from each other ; in the geranium they slightly adhere 

 at the base (fig. e) ; in the mallow they adhere into a tube, except 

 near the upper extremity, where they are not united, and have their 

 ordinary appearance (fig. /) ; in other plants they grow together into 

 a solid tube hi which no trace of separation can be discovered, as in 

 thf genus Guarea (fiy. y). 



Finally, in the pistil there are certain parts called carpels, each of 

 which is a hollow body terminated by a style and stigma. These 

 carpels are hollow, because they are formed of a flat organ, doubled 

 up so that its edges come in contact and adhere to each other. 

 Sometimes only one carpel is present in a flower, as hi the cherry 

 ( li-i. A) ; sometimes several, as in the rose (fiy. i). In the A'lgeUa, the 

 styles of the carpels are all distinct (fig. k), but in the lily and 

 the myrtle (fig. I ) the styles of the carpels adhere so completely that 

 there seems to be but one. In the apple, the calyx seems to grow 

 from the top of the fruit ; this is caused by the carpels having at a 

 very early period adhered to the inside of the calyx, which afterwards 

 grows with their growth, and, finally, leaves its extremities in a 

 withered state near the top of the carpels : in the cherry, on the 

 contrary, no adhesion ever takes place between the carpel and 

 the calyx ; and, consequently, when the fruit is ripe, there is no trace 



of the latter upon its upper end. In the raspberry, the fruit is 

 enabled to slip like a thimble from off the receptacle, because the 

 carpels all adhere by then- sides. 



(De Candolle, TMorie El&nentaire de la Sotanique; Lindley, Intro- 

 duction to Butany ; Schleiden, Principles of Scientific Botany.) 



ADIANTUM (aSia.noi/), a genus of Ferns, so called by the Greeks 

 because the leaves are of such a nature that water will not readily 

 moisten them. The plant described by Hippocrates and his successors 

 under this name appears to have been the A. Capillus Veneris, or 

 the Maiden-Hair Fern a rare European species, occasionally met with 

 on moist rocks, and old damp walls, even in this country. From 

 other genera of the same tribe it is known by its size, or masses 

 of reproductive particles, being situated upon the margin of the 

 leaves, and covered over by a thin curved scale which separates from 

 the leaf by its inner edge. 



The number of species is very considerable, probably not far from 

 80 or 90, and, as is the case in all extensive genera of Ferns, 

 comprehends every degree of division of the leaves, from perfect 

 simplicity to the most compound conditions. All those in which the 

 leaves are much divided are remarkable for the very delicate elastic 

 stalks on which the broad leaflets are attached ; it is to this circum- 

 stance that the name of Maiden's Hair has been given to the European 

 species. The genus is scattered over all the world, from Europe to 

 New Zealand, but is not found in any high latitudes in either 

 hemisphere. By far the greater part of the species inhabit damp 

 tropical wpods. 



A. Capillus Venerii is a dark-green stemless plant, found in damp, 

 rough rocky places, by the side of water-courses, and on the edge of 

 wells, where the air is keen and dry. Its leaves, which are from six 

 to fifteen inches high, have a blackish-purple highly-polished stalk, 

 divided into a great number of very slender ramifications, from the 

 extremities of which proceed the thin, delicate, wedge-shaped leaflets, 

 which are notched irregularly upon their upper edge, and have the 

 most graceful appearance imaginable when growing a little above 

 the eye, and gently agitated by the wind. Wonderful medicinal 

 properties were once ascribed to this species, but they have long since 

 been discovered to have no existence except in the exaggeration of 

 fanciful practitioners. All that can be discovered in it is a slight 

 but pleasant aromatic flavour ; the French occasionally use it in 

 slight coughs. Cap-Main is prepared by pouring boiling syrup upon 

 the leaves of this species, or of A. pedatum, an American plant of 

 larger growth and far less divided leaves ; a little flavour is afterwards 

 given with orange-flowers. 



ADINOLE, a laminated variety of Felspar, sometimes called 

 Fusible Hornstone, Leelite, and Petro-silex. [FELSPAR.] 



ADIPOSE TISSUE is usually associated with Areolar Tissue 

 [AREOLAR TISSUE], the two being generally known collectively as 

 Cellular Tissue. It must be distinguished from Fat [FAT], adipose 

 tissue being a membrane of extreme tenuity in the form of closed 

 cells or vesicles, while fat is the material contained within them. The 

 membrane of the adipose vesicle does not exceed the 20,000th of an 

 inch in thickness, and is quite transparent ; it is moistened by watery 

 fluid, for which it has a greater attraction than for the fat it contains. 

 Each vesicle is a perfect little organ, varying, when fully developed, 

 from the 300th to the 800th of a line ; minute capillaries may be 

 observed on their external surface. (Fig. 2). When fat-vesicles are 

 deposited together in large numbers, as is usually the case, they assume 

 a more or less regular polyhedric form from their mutual pressure. 



When the first traces of fat appear is not accurately known. In a 

 well-formed five-months' human foetus, Valentin found in the subcuta- 

 neous cellular tissue of the sole of the foot not merely fat cells, such 

 as occur hi adults, varying from the ordinary size to the 125th or 

 100th of a line, within and around which were numerous small vesicles 

 (fig. I, a), but other forms which threw more light on their structure 

 and development. In some the surrounding cell-membrane was much 

 more distinct than as it occurs in adults (A). In others there appeared 

 to be a deposition of fat, not occupying the whole space of the cell (c) ; 

 the remainder of the cell having often a striped or streaky appearance, 

 and forming a lateral projection ; this is seen in c, and in a more 

 marked degree hi d and e. In other fat-cells there were observed to 



