founded on the Structure of their Seedlings. 75 
culty within the cotyledonary tube, and their habit is not 
dissimilar from that of seedlings with distinct cotyledons. 
Short petiolar tubes are not uncommon among the seed- 
lings of species allied to those included in Table I. For 
example : Ranunculus millefoliatus (Irmisch, 26, p. 29, Fig. 1), 
Ferula foetida (Lubbock, 30, II, p. 37), Serratida tinctoria 
(Winkler, 41) Cotula coronopifolia (Lubbock, 30, II, p. 134), 
and Rheum officinale (Lubbock, 30, II, p. 442, Fig. 622). 
They link the numerous species in which the cotyledons are 
merely connate at the base with those in which the cotyle- 
donary tube is fully developed, and their existence is a strong 
argument for the derivation of such tubes from the fusion 
of two cotyledons, and not, as Professor D. H. Campbell has 
suggested (7, p. 11), from the division of one. 
From the first class of seedlings with united cotyledons we 
may now pass to the second. Ranunculus Ficaria and Anemone 
apennina (Sterckx, 38, pp. 34 and 80, Figs. 76, 77) are the 
only species with which I am acquainted in which the 
cotyledons are normally united by one margin only. Such 
unions are, however, not unfrequently found in abnormal 
specimens of species with distinct cotyledons. Ranunculus 
repens (Lubbock, 30, I, p. 90, Fig. 129) and R. Chius have 
been mentioned already. Irmisch found this abnormality in 
several seedlings of Phlomis tuherosa (22, p. 25, Fig. 105). 
Mrs. Stebbing has shown me a drawing of an abnormal 
seedling of Urtica dioica in which the blades as well as the 
short petioles of the two cotyledons are united by one margin. 
No doubt such instances could be multiplied. Their interest 
lies in the possibility they suggest that the single seed-leaf 
of some species among those Dicotyledons which possess but 
one may be formed in a similar way. 
The seed-leaf of Pinguicula vulgaris , for example, looks in 
Buchenau’s figures (6, Figs. 1 and 2) as if it might be derived 
from the union of two cotyledons by one margin only. 
Dickson (11) states that P. grandiflora also germinates with 
a single seed-leaf, the blade of which is bifid. P . caudata and 
P. lusitanica have separate cotyledons. 
