THE ROOT-SYSTEM OF IMPATIENS ROYLEI. 493 
Observations on the Root-System of Impatiens Royle: *, Walp. Ву ISABEL 
M‘Craronte, B.Se. (Research Scholar in Botany, University College, 
Nottingham). (Communicated by H. S. Horpen, M.Sc., F.L.5.) 
(PLATES 37, 38, and 24 Text-figures.) 
[Read 14th December, 1916.] 
Introduction. 
Гмратгвхз Ёоүвит, Walp., is а hardy annual of Indian origin which, owing 
to its very efficient seed-dispersal mechanism, spreads rapidly. It is difficult 
to eradicate, and tends to become a troublesome weed. ‘The plant is common 
in the Midlands, and occurs in extensive beds in neglected gardens in which 
it has gained a footing. In these crowded areas the plants rarely reach their 
full development : the tallest specimens do not exceed one and two-third 
metres, and the lateral branches are smal] and lacking in vigour. А well- 
grown solitary plant may attain a height of three metres, measure six 
centimetres in diameter at its base, and possess well-developed branches, 
these being borne in whorls of three or four. 
The plant shows for its size a remarkably poorly developed vascular 
system, the xylem even in large plants forming only a thin ring, so that 
mechanical efficiency is almost entirely due to the turgid parenchyma. The 
nodal regions are usually dilated, as are the bases of the lateral branches, so 
that prominent bulges are produced, these being particularly noticeable in 
well-developed branches. 
Primary Root-System. 
The seeds of inpatiens Roylei germinate in late April or early May, the 
seedling being of the normal dicotyledonous type, and having a primary root- 
system consisting of a tetrarch tap-root and tetrarch or pentarch lateral roots. 
The hypocotyl varies greatly in length according to the depth at which the 
seed is buried (Pl. 37. figs. 1, 2, & 3) and, when it is long, lateral roots of 
hypocotyledonary origin are sometimes developed ; these roots are always 
subterranean and usually show no regularity in succession and appearance 
(РІ. 37. fig. 4). An exceptional case is shown in РІ. 37. fig. 5, where the 
roots are in a distinct whorl just below the soil-level. 
In the majority of the seedlings examined there is an abrupt narrowing of 
the axis at the junction of hypocotyl and tap-root, and at this point the tap- 
root, which is always relatively short, bears a whorl of four strong lateral 
roots of equal or greater length than itself (Pl. 37. fig. 5). In other seedlings, 
ж Т am indebted to Dr. O. Stapf, F.R.S., for confirmation of this determination. 
LINN. JOURN,—BUOTANY, VOL. XLII, 20 
