Ranales , Rhoeadctles , and Rosales . 
723 
to the central double bundle, lateral which is on opposite sides in the 
two cotyledons. These laterals pass into the hypocotyl, where they persist 
lower down than the plumular tissue, but ultimately die out, and the root 
is diarch. This phenomenon is suggestive of tetrarch relationship. 
Potentilla chrysantha and P. fruticosa. These species show the usual 
arrangement associated with the diarch type. The plumular traces, which 
are distinctly double, are inserted rather low down, and in P. chrysantha 
the cotyledon strands pass out asymmetrically into the base of the fused 
cotyledons. 
Frag aria indica . The very slender seedlings of this species show 
similar features to those in the Potentillas described. 
Geumcanadense , G.urbanum , G.coccineum , G. japonicum, and G. monta- 
num. Very slender seedlings possessing high transition and diarch root. 
In one individual of G. canadense an interesting variant was provided by 
the presence of a small strand in the intercotyledonary plane, which passed 
out as a single cotyledonary lateral. 
Rhodotypus kerrioides . This seedling has a more robust habit, but it 
conforms in a general way to the diarch type. The process of root forma- 
tion is, however, very much delayed throughout the long hypocotyl, and 
even much below the collet the root has a large central pith. The hypocotyl 
is characterized by four widely separated metaxylem masses lightly bridged 
in the cotyledonary plane by the protoxylem strands, and the general form 
is reminiscent of Rubus. 
Spiraeoideae. 
Spiraea callosa is an extremely minute form, showing the simplest 
possible production of a diarch root by the fusion of the double bundles 
at the cotyledonary node. 
Exochorda grandiflor a and E. Albertii possess far more robust seedlings 
than the Spiraeas, but the transition features are essentially the same. 
The details, however, recall slightly those of Rubus and Rhodotypus. 
Pomoideae 
Pyrus communis , P. Malus, P. Aria, P. Aucuparia. These species pre- 
sent considerable variation, and furnish proof of the unimportance of the 
independence or non-independence of the laterals, since not only do both 
conditions occur within the genus as in Prunus , but even within the species, 
e. g. P. communis . The hypocotyl possesses four or six protoxylem groups 
with alternating phloem strands arranged in the usual triad manner. The 
group in the cotyledonary plane is continuous with the double bundle of 
the petiole as always, and the one intercotyledonary or two diagonal groups 
3 c 
