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219 
very great and bends first downwards, then up, removing the insertion 
of the lateral sepals and labellum to a distance from the column. 
Acanthophoenix H. Wendl. Palmae (iv. 6). 3 sp. Mascarenes (p. 195). 
Acanthophyllum C. A. Mey. Caryophyllaceae (1. 2). 18 sp. W. As., 
Siberia. Mostly desert xerophytes with prickly leaves (see p. 167). 
Acanthorhiza H. Wendl. Palmae (1. 2). 4 sp. trop. Am. The 
adventitious roots that spring from the lowest nodes grow normally 
downwards into the soil, but those from the nodes above develope 
into numerous thorny branches, and never reach the earth (pp. 39, 40). 
Acanthosicyos Welw. Cucurbitaceae (111). 1 sp. S.W. Afr., A.horrida 
Welw., the Narras, a remarkable plant growing on sand dunes (cf 
Welwitschia, and see p. 195). The root, several inches thick, is very 
long (up to 40 ft.). Above ground is a thorny shrub, about 3 ft. high, 
with long tendrils; the thorns are modified twigs. The fruit is 
eaten by Hottentots. (See Welwitsch, Trans . Linn. Soc. 27, 1869.) 
Acanthospermum Schrank. Compositae (v). 3 sp. trop. Am., W. Ind. 
Acanthostachys Link, Klotzsch, et Otto. Bromeliaceae (1). 1 sp. (A. 
strobilacea L. K. et O.), Brazil, usually placed in Ananas. 
Acanthus Tourn. ex Linn. Acanthaceae (iv. B). 20 sp. trop. and sub- 
trop., As., Afr., Eur., mostly xerophytes with thorny leaves (those of A. 
spinosns L. furnished, it is supposed, the pattern for the decoration of 
the capitals of Corinthian columns). A. ilicifolius L. forms part of 
the mangrove vegetation of trop. As., Afr., &c. (p. 19 1). FI. a large 
bee-flower ; there is no upper lip to the corolla, and the protection of 
.the pollen, &c. is undertaken by the calyx. The anthers form a box 
by fitting closely together at the sides, and shed their pollen sideways 
into it, where it is held by hairs till an insect probing for honey forces 
the filaments of the sta. apart and receives a shower of pollen on its 
head (cf. many Scrophulariaceae, Ericaceae, &c.). In the young flr. 
the style is behind the anthers, later on it bends down so as to touch 
a visiting insect. The frt. explodes and there are large ‘jaculators’ 
on the seeds. 
Acer (Tourn.) Linn. Aceraceae. no sp. N. temp., esp. in mountain 
of hill districts (A. psetidoplatanus L., the sycamore, and A. campcs- 
tris L., the maple, in Brit., the latter native) and trop. mts. There 
are many sp. in S.W. China and Japan. Trees and shrubs, with opp. 
exstip. leaves, deciduous or evergreen. Leaf in some simple entire, 
more commonly 3- or 5-lobed, occasionally compound. An interest- 
ing exercise is to go through a collection of A. in an herbarium or 
elsewhere, comparing the leaf- tips as to degree of development of the 
acuminate “drip-tips” (cf. Ficus, and see p. 143) noting at the same 
time the kind of climate from which each specimen has come. There 
is a good general correlation between the length of tip and wetness 
of climate. 
Large winter buds are formed, covered by scale leaves. In many 
sp. transitional forms may be seen as the bud elongates in spring (cf 
p. 20), between the scales and the green leaves, showing that the 
