URTICACEJS. 513 



great height ; for instance, in Laportea gigas, 1 which may attain one 

 hundred feet, the dots of the woody fibres and vessels are surrounded 

 by a concave areola, which, with that of the neighbouring fibre, forms 

 a lenticular chamber, comparable to that found in many trees of 

 various orders. 2 



The affinities 3 of the order Urticacece are numerous. We have 

 mentioned 4 its close ties with Piperece, and shown how it is chiefly 

 distinguished by the organization of the fruit, seed, and embryo ; it 

 also differs in the manner of inflorescence, and its perianth and 

 properties. All the secondary groups formerly united with this into 

 one immense common order, and now separated into Cannabinece, 

 Morece, Artocarpece, Ulwacece, Celtidece, are, no doubt, most nearly 

 related to it. But they are constantly separated, generally speaking 

 by the presence of two carpel lary leaves, united into a two-celled 

 ovary, with one cell sometimes sterile, often distinct towards the top 

 of the style, and connected below by an axile placentary column, 

 which is inserted on either side an ovule more or less decidedly ana- 

 tropous and descending. It is by an analogous character that 

 Urticacece are far removed from many Polygonacece, Salsolacece, &c, 

 with which they have been compared. 5 In all these plants the basilar 

 or free central placenta bears more than one carpellary leaf. But in 

 Urticacece the gynaeceum is unicarpellary, as in Ceratoplnjllece and 

 Piperece, to which botanists have rightly noticed their relations, 6 and 

 as in Ngctagi/tece, distinguished from this order chiefly by their often 

 petaloid perianth and their anatropous ovule. The latter character 

 also extends to several unicarpellary Phytolaccacece. Weddell has 

 chiefly compared the present order to Tdiacece and Maloacece, consider- 

 ing it especially as a reduced type of the former/ like Buettneriece may 

 be said to have a reduced type in Etiphorbiacece. The last-named order 

 shows in certain cases such close analogies in habit, foliage, and 



1 Wedd., Monogr., 129, t. 3, 4; Prodr., 82, 311) presumes that this is exceptional in the 

 n . \\.— Urtica gigas A. Cunn., hiss. — Urera order. 



excel'sa Wedd., in Ann. So. Nat., ser. 4, i. 178.— 3 Wedd., Monogr., 32. 



U. rotumdifolia Wedd., loc. eit. 4 See p. 4S6. 



2 Wedd., Monogr., 131, t. 4, figs. 1-9. The 5 Lindl., Veg. Kmgd., 261, 262. 

 bark contains, besides liber fibres, large oblong « Lindl., loc. eit., 264. 



cells filled with acicular or prismatic raphides of 7 See, for the development of this proposition, 



oxalate of lime (tig. 2). Guillakd {loc. eit., his Monographic, 35-41. 



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