178 ON SEEDLINGS 



that of the latter is widely and shallowly crenate. P. den- 

 ticulata is also notable for the shortness of its hypocotyl 

 and the length of the petioles of the cotyledons which com- 

 pensate for this deficiency. The cotyledons of P. elatior 

 (fig. 497) differ in being ovate-oblong and trinerved. The 

 first leaf is reniform, and the second is rotund-cordate ; both 

 are dentate. The cotyledons of Androsace rotundifolia 

 on the other hand are broadly ovate and short. The first 

 leaf is somewhat triangular and entire or tridentate ; 

 and succeeding ones vary between reniform and orbicular, 

 palniately nerved and lobed. A modification of the ovate 

 type occurs in P. vulgaris and P. sinensis. Those of the 

 former (fig. 498) are ovate, emarginate, three- or faintly five- 

 nerved, and finely glandular-pubescent. The first two leaves 

 are ovate. This species is remarkable for the behaviour of 

 the radicle and hypocotyl under different conditions and in 

 different soils. In sand the radicle strikes down vertically, but 

 in soil of a stiffer nature it generally grows along the sur- 

 face for some little way before striking downwards, and the 

 hypocotyl generally bends in the same way and throws out 

 lateral rootlets, abundantly provided with root-hairs. The 

 radicle soon ceases to elongate and, gradually dying away as a 

 procumbent stem or rhizome is formed, gives rise to the 

 popularly so-called praemorse root. The cotyledons of P. 

 sinensis (fig. 499) are normally broadly ovate and emarginate, 

 but they frequently behave in an irregular manner, one of 

 them often being bifid or bipartite and sometimes divided 

 to the base of the petiole making apparently three cotyledons. 

 In those that are bifid the midrib becomes forked at some 

 distance below the sinus. Both cotyledons are bifid -in some 

 cases ; and they are coarsely hairy and glandular. The 

 primary leaves are cordate and more or less lobed and toothed. 

 A second type is met with in Soldanella. The cotyledons are 

 oval and obtuse at either end. The first three leaves are 

 reniform and entire. Spathulate cotyledons are met with in 

 Androsace nana. The primary leaves are narrower, linear- 

 lanceolate, entire and arranged in a dense rosette. Those of 

 Asterolinum splendidum are similar in shape but opposite and 

 decussate, with the internodes more elongated. The cotyledons 



