the Genus Hottonia. 
255 
A whorl of the characteristic pinnate leaves always occurs beneath the 
circle of branches, but along the length of the stem the insertion is very 
irregular. More than one is often found at a node, but Kamienski ( 7 ) states 
that they are spiral, and has calculated a divergence of § for them. On 
the inflorescence axis the simple, entire bracts are certainly borne several 
at a node. The flowers are very similar to Primula in structure, with the 
trifling exception that it is in the short-styled forms that the stigma is found 
at the mouth of the corolla tube, while in the long-styled it projects. 
Cleistogamy has been attributed to Hottonia , but I have found no trace of 
it during three summers’ field work. The idea is probably due to some 
small, closed flowers, which occur sometimes among those fully developed, 
but serial sections have shown that these are merely abortive. 
The foregoing description applies also in the main to H. inflata , which 
differs chiefly from our own species in possessing a whorl of lateral inflores- 
cence axes at the base of the terminal shoot. These take the place of the 
vegetative branches of //. palustris , though they are not horizontal, but rise 
nearly to the height of the main axis. The internodes are greatly swollen 
by the enlargement of the pith cavity, and if the general habit of the two 
species is similar, this reduction in the specific gravity may compensate for 
the loss of the aquatic branches. The material at my disposal was, how- 
ever, confined to three specimens (kindly obtained for me by Dr. Coulter) 
which had passed through the post, and I therefore have no data for such 
points as the correlation of structure and function, the occurrence of land 
forms, &c. 
II. Anatomy. 
In the young plant of PL palustris , and occasionally in the very oldest part 
of the mature plant, the simplest type of stele is found, consisting of a central 
strand of xylem, surrounded by phloem, pericycle, and endodermis (Diag. 1, 
p. 2 56, and Fig. 21, PI. XXI). With these exceptions a pith 1 is always present 
(Diag. 2), though it varies greatly in size, both in individuals and in different 
parts of the same plant. A cambium may usually be clearly distinguished 
(cf. Text-fig. 2), but there is little or no trace of secondary thickening. The 
cortex is lacunate, and in the subterranean stem, particularly in the thickly 
rooted parts, the three or four innermost layers often stain differently from 
the rest and are very regularly arranged round the endodermis ; the con- 
stituent cells are tangentially elongated and fit closely with or without 
minute quadrilateral spaces between them (Fig. 12, PL XX). Thus in its 
underground part Hottonia shows an anatomical point of agreement with 
the terrestrial Primulas (cf. Gwynne- Vaughan ( 5 ), Fig. 1, PL XIV, and 
Solereder ( 10 ), p. 506, and Fig. 115 b). 
Except in the subterranean stem, the epidermis bears numerous 
1 The term is used descriptively ; its nature will be referred to later. 
