75 369 



From p. 305 onward, tlie writer deals witli a series of examples of species having» under- 

 ground runners, suboles, chiefly taken from the northern flora. 



1. Underground runners not combined willi nutritive reservoirs; p. 305. 



A. Herbaceous plants with orHiotropic shoots (nol climbing); p. 305 — 320. 



B. Herbaceous lianas with suboles; p. 320—323 



C. Ligneous plants with underground runners; p. 324 — 327. 



D. PoUacanthous herbs with rosette; j). 327—330. 



E. - — semi-rosette; p. 330-334. 



F. — — graminoid shoot; 335 — 337. 



II. Suboles with nutritive organs; p. .337. 



A. The potato type; p. 357. 



B. Suboles with fleshy roots; p. 344. 



C. — -- bulbs; ]). 347. 

 Summary; p. 348. 



The following observations may be made as to underground runners in general. 



The length of the intern odes is distinctly dependent upon the resistance and 

 moisture of the soil. The longest and most extended suboles are found in loose sandy soil, 

 loose, moist forest mould, lield and garden soil, and mud. Soil such as the stiff clay of the 

 South American savannahs has but very few species witii underground runners, and the 

 runners themselves are short; tliere are, on the other liand, many si)ecies with tussock- 

 growth and what Lindman has called "xylopodia", i. e thick and lignified mesocormes 



The buds of the underground runners have, in addition to the usual function of a 

 bud —, that of protecting the growing point and embryonic tissues of the stem against exsic- 

 cation, — also the unusual task of forcing a way through the earth. The manner in which this 

 is done had been previously described by Ortmann, Warming and Massart, and, as regards 

 the erect shoots of the mesocorme and other earth-stems, by Areschoug and Massart. They 

 are as follows: a) The leaves decussate or verticillate: the uppermost leaves close up into 

 an often pointedly conical body (see figs. 5, (i, 9, 10, 11, 13, 14, 15, 16, 33). b) Leaves scattered: 

 the scales place themselves one over the other, at times they may be almost hood-shaped 

 (figs. 3, 18, 24 and others quoted on p. 351). In species of the grass type and other monoco- 

 tyledons, they roll up into a cornet and can, in certain grasses etc., form a positively ])iercing 

 body (figs. 30, 31, 38 and other figures quoted on p. 351). c) The most interesting adaption is 

 the hooked curvature of the apex of the stem; the young leaves of the bud can lie quite loose, 

 with the i)oints turned u))ward, as the bud turns backward, and the work of forcing a pas- 

 sage is left to older parts of the stem. In most cases, the end of the runner suddenly be- 

 comes much thinner immediately before the curvature begins; this shows that is it not 

 altogether a purely mechanical curving of the stem end which has taken i)lace (figs. 1, 19, 

 21, 22, 23, 26, 36, 37, 45). Quite recently Salisbury (1916) has referred to the anatomical diffe- 

 rence between the tissues of the concave and those of the convex side. This hooked curva- 

 ture is, as we know, common also in seedlings, and likewise in the stalks of leaves (see 

 Klebs, Abeschdug 1895, Massart, Rai:nki.î;r 1905). 



Roots (J). 352). In the first i)lace, there are roots at the nodes, often placed in a very 

 deflnite arrangement in relation to the leaves; in some species, especially the l^ricima', in 

 the axil of the leaf itself. (See figs. 2, 24, 25, 26, etc. Also Warming 1877; 80, 1908 figs. 19, 38, 

 39). In some underground runners, roots are also found on the internodes, without any- 

 ordered arrangement. 



That the roots so generally are associated with the base of the leaves is natural, since 

 the formation and nourishment of the axillary branches is thus facilitated. Most roots grow 

 downwards, but some also up, these being, however, generally thinner and shorter, probably 

 owing to the effect of gravity. The number and strength of the roots in underground run- 

 ners will be in inverse proportion to the strength and longevity of tlie primary root. 



49* 



