Observations on the Anatomy of Teratological 
Seedlings. 
III. On the Anatomy of some Atypical Seedlings of 
Impatiens Roylei, Walp. 
BY 
H. S. HOLDEN, M.Sc., F.L.S., 
University College , Nottingham. 
With one hundred and thirteen Figures in the Text. 
/ . MPATIEN S ROYLEI is an annual of Indian origin which has become 
naturalized in England, and which, when once intrq^nced, rapidly 
colonizes patches of bare ground unless thoroughly eradicated. A plot of 
ground in the garden of the University College, Nottingham, is completely 
covered with the plant in question, and it is from this source that much of 
the material for the present investigation has been derived. A further 
supply of seedlings has been obtained from the gardens of friends in 
Plymouth, the total number examined being sixty-one. It is proposed first 
of all to give some account of the vascular anatomy of the normal seedling 
and the young epicotyl, and then to show how these have been modified in 
the atypical specimens studied. 
i. The hypocotyl of the seedling , at the time that the first epicotyle- 
donary leaves become obvious, is about five centimetres in length and bears 
two somewhat fleshy, heart-shaped cotyledons with stout petioles which 
occasionally unite basally to form a very short cotyledonary tube. At the 
junction of the hypocotyl and root is a whorl of four stout rootlets below 
which the main root thins considerably (Figs, i, 2, and 3). This whorl of 
roots, which is initiated at a relatively early stage in the development of the 
embryo, is very characteristic and forms a useful basis of comparison in 
studying the abnormal seedlings. A similar root whorl has also been 
described in Impatiens Balsamina by Chauveaud ( 1 , p. 334). 
In most seedlings the vascular supply of each cotyledon consists, at the 
proximal end of the blade, of a median endarch xylem group with a mass 
of phloem on either flank, and a pair of lateral bundles; this system giving 
rise to a tetrarch hypocotyledonary grouping, and in the root to a solid 
tetrarch xylem star with the usual radial arrangement of the phloem. 
In the very young seedling (Fig. 1) exarchy is evident a little way 
[Annals of Botany, Vol. XXXIV. No. CXXXV. July, 1920.] 
