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14 



ACROCARPI. A division of mosses con- 

 taining those species in which the female 

 fruit terminates the branches. Unfortu- 

 nately even in the same genus, as Fissidens, 

 species with lateral and terminal fruit 

 occur, so that the distinction is not with- 

 out grave exceptions. [M. J. B.] 



ACROCARPIDIUM. The plants constitut- 

 ing this genus of the natural order Piperacece 

 are closely allied to those included in the 

 genus Peperomia, from which they differ 

 in habit and in the pseudo-pedicellate fruit. 

 They are for the most part creeping plants, 

 growing upon trunks of trees or mossy 

 banks, with hairy or smooth, alternate 

 roundish or kidney-shaped leaves, which 

 have three or five prominent nerves ; the 

 flowers are placed in rings on long-stalked 

 catkins with somewhat fleshy bracts ; they 

 have two distinct stamens, a simple stigma 

 crowning the stalkless ovary, which latter 

 ripens into a fruit so contracted at its base 

 as to give an appearance as if it were 

 placed on a stalk. They are natives of tro- 

 pical America and the West Indies, and 

 partake in some degree of the general 

 cordial properties of the family to which 

 they belong. A. hispidulum is made use of 

 in the West Indies as a bitter and sto- 

 machic. Several kinds are cultivated in 

 stoves as objects of curiosity or of botani- 

 cal interest rather than for their beauty. 

 They are best known under the old name 

 of Peperomia. .[M. T. MJ 



ACROCH^JTE punctata. An epiphytal 

 orchid from the Sikkira Himalaya, where 

 it was found by Dr. Hooker at the height 

 of 4,000 feet above the sea. It has an ovate 

 pseudo-bulb, a long solitary coriaceous leaf, 

 and an erect radical inflorescence. The 

 flowers are straw-coloured, dotted with 

 crimson. It is nearly related to Sicnipia, 

 with which it agrees in having a couple of 

 long taper caudicles for the pollen masses. 



ACROCLINIUM. A beautiful genus of 

 annual composites, at present represented 

 in our gardens by the A. roseum, recently 

 introduced from the Champion Bay dis- 

 trict, Western Australia. Its flower-heads 

 resemble those of the well-known Rho- 

 dantJie Manglesii, but are larger, and the 

 habit of the plant is entirely distinct. It 

 produces numerous erect unbranched stems 

 a foot or more high, the primary one emit- 

 ting two opposite shoots from its base, 

 each of which in their turn throws out 

 two additional ones, which again become 

 the parents of others, until the plant as- 

 sumes a bushy character. The stems are 

 clothed with numerous linear, smooth, 

 pointed leaves, and bear at the summit a 

 sinarle handsome flower-head an inch and a 

 half in diameter, consisting of a bright 

 yellow disk of tubular florets, surrounded 

 by a many-leaved, imbricated involucrum, 

 the innermost leaflets of which have 

 spreading rose-coloured tips, presenting, 

 as in Ehodanthe, Helichrysum, and other 

 allied genera, the appearance of ray florets. 

 The fruit, or, as it is popularly but in- 

 correctly termed, the seed, is clothed with 



j snow-white silky down, and is surmounted 

 by a pappus of from fifteen to twenty 



\ feathery hairs or scales, flattened and con- 

 nected at their base, and tipped with a 

 yellow tassel-like brush, by which charac- 

 ters the genus is chiefly distinguished. The 

 yellow colour of the disk is due less to the 

 colour of the florets themselves than to the 

 brush-like tips of the pappus hairs, which 

 under a lens are very interesting objects. 

 Four other species occur in the same lo- 

 cality, but do not appear to have been yet 

 introduced. [W. T.] 



ACROCOMIA. The name given to a 

 genus of palms, in allusion to the elegant 

 tufts of leaves at the summit of the stem. 

 One species, A. sclerocarpa, grows almost 

 all over South America, occurring in dry 

 soil, rarely in woods. The tree belongs to 

 the same tribe as the cocoa-nut palm ; its 

 trunk rises to twenty or thirty feet in 

 height, and is sometimes swollen in the 

 middle ; the leaves are from ten to fifteen 

 feet in length, pinnate, with from seventy 

 to eighty leaflets on each side. The young 

 leaves are eaten as a vegetable. It is culti- 

 vated in our hothouses. [M. T. M.] 



ACROGENS. A large and most important 

 division of Cryptogams, distinguished 

 for the most part from Thallogens, as 

 Funguses, Seaweeds, and Lichens, by their 

 herbaceous growth, the presence of leafy 

 appendages which are frequently furnished 

 with stomates, the different mode of im- 

 pregnation, and the presence of vascular 

 tissue. A few acrogenous Liverworts have 

 the habit of Lichens, but differ totally in 

 structure. 



The most important distinction, however, 

 undoubtedly is that the impregnation takes 

 place somewhat after the manner of Ph^;- 

 nogams, by an impression made upon the 

 contents of the embryonic sac, and not upon 

 the spore itself, as is decidedly the case 

 amongst Thallogens where the mode of 

 impregnation has been ascertained, as 

 in Algce. In Cliaracece alone the spore 

 seems to be immediately impregnated, 

 though even in this case it is uncertain 

 whether impregnation does not take place 

 before the spore is perfected. 



In Mosses, Liverworts, and Ferns, the 

 spore after germination produces at first 

 either a web of threads, a solid mass, or a 

 membranous expansion (prothallium). In 

 the two former a distinct plant arises from 

 the threads with frequently symmetrical 

 leaves, and on these plants urn-shaped 

 organs are produced (called archegones) 

 analogous to pistils, which contain at their 

 base a cell which, after impregnation, pro- 

 duces the proper fruit. In perennial spe- 

 cies a fresh crop of archegones may be 

 produced in two or three successive years, 

 which require a distinct act of impregna- 

 tion for the development of the capsules. 

 In Ferns and their allies, on the contrary, 

 the archegones give rise to a new plant, 

 which for one or for many successive years 

 produces a fresh crop of fruit without fur- 

 ther impregnation. The result of impreg- 

 nation in the two cases, then, is quite 



