548 ON SEEDLINGS 



to occupy the space on each side of the radicle, which terminates 

 abruptly in three rounded lobes. The reason for this peculiar 

 form of the radicle is not very evident. The seed in transverse 

 section is thinly elliptic. 



Seedlings. At least two well-marked types of cotyledons 

 occur as well as a few striking exceptional instances. One 

 type is represented by Cuphea silenoides (fig. 354). The 

 cotyledons are roundly-triangular, emarginate, truncate at 

 the base and faintly five-nerved. A remarkable point about 

 them is that they are auricled at the base while still in the 

 seed as above noticed, and for some time after germination ; 

 but as growth proceeds and they become fully developed the 

 auricles become lost or obliterated by the more rapid growth 

 of the lamina in the neighbourhood of their attachment to 

 the petiole than in the auricles themselves. Similar examples 

 are met with in species of Salvia belonging to the Labiatse, 

 but the obliteration of auricles already well- developed in the 

 seed is by no means of frequent occurrence. They usually 

 increase in size after germination. The primary causes of 

 the auricles, and the emargination, are referred to above. 

 The abrupt and sublobate condition of the hypocotyl in the 

 seed shows itself after germination in the form of an annular 

 thickening. C. Eoezlii agrees generally with the type given, 

 but the cotyledons are much smaller and subcuneate at the 

 base when full grown ; and the latter characteristic is no 

 doubt due to growth subsequent to germination. This is 

 carried to a still greater extent in Cuphea coccinea where the 

 cotyledons are broadly obcordate with a cuneate base and 

 trinerved. The first pair of leaves in all three cases is ovate 

 and entire, and subsequent ones vary between oblong-elliptic 

 or lanceolate, or remain unaltered except in size. 



The second type is met with in Lythrum flexuosum and 

 other species which have oblong-oval, obtuse cotyledons with 

 a cuneate base. In L. flexuosum they are small, often slightly 

 constricted near the apex and appearing obsoletely trinerved. 

 Venation seems restricted to a faint midrib. The primary 

 leaves at least are opposite, oblong-ovate, and decurrent on 

 the stem, making it quadrangular or narrowly four- winged. 



An exceptional case to the above types is met with in 



