320 J. Holm — North American Species of Stellar ia. 



small, fleshy, scale-like leaves (fig. 3). In specimens from 

 lower altitudes the stems are taller, and the inflorescence is an 

 amply ramified cyme, beside that the stolons are much longer 

 with the internodes stretched, almost to the same extent as in 

 the species described above. 



The internal structure of the alpine plant is quite character- 

 istic ; the green leaves have a larger number of stomata on the 

 ventral face than on the dorsal, and these are surrounded by 

 four or five ordinary epidermis-cells ; they are level with epi- 

 dermis, and the air-chamber is wide, but shallow. In most of 

 the other CaryojjhyllacecB the stomata are surrounded by two 

 subsidiary cells, which are arranged vertical on the stoma.* 

 The chlorenchyma consists of a typical palisade-tissue of one 

 or two layers, and an open pneumatic tissue below this. There 

 is a small, thinwalled water-storage tissue on the leptome-side 

 of tl>e midvein, but in regard to the mechanical tissues we find 

 only a very few, thinwalled stereome-cells on the dorsal face of 

 the midvein, but inside the parenchyma-sheath. The leaves 

 of the stolons have, of course, no stomata, and the chloren- 

 chyma represents a homogeneous tissue of roundish cells filled 

 with starch, and very compact ; the veins are, also, here sur- 

 rounded by thinwalled parenchyma-sheaths, and lack mechan- 

 ical support. 



The aerial stem has a thickwalled epidermis with promi- 

 nent, longitudinal ridges on the outer cell-wall, covered by a 

 thick, smooth cuticle ; the cortex is quite compact, and a thin- 

 walled endodermis surrounds apericycle of slightly thickwalled 

 stereome. The stele consists of an almost continuous zone of 

 leptome and hadrome, with a central pith of moderately thick- 

 walled cells. A corresponding structure is to be observed in 

 the subterranean axes, the stolons, but the pericycle is here 

 very thinwalled, and the stele is composed of four separate 

 mestome-strands and a broad, central pith. 



This peculiar method of hibernation is thus characteristic 

 of species that occur under very extreme climatologic condi- 

 tions: in the far north, and on the summit of high mountains. 

 We now pass to describe the third type of vegetative reproduc- 

 tion, in which a strongly developed rhizome occurs, and in which 

 the aerial stems are strictly annual. This type is represented by 



Stellaria Jamesii Torr. 



This species is an inhabitant of the wooded belts of the Rocky 

 Mountains in Colorado. The slender stem is terminated by a 

 large, leafy cyme, and the lower stem-leaves subtend short, 

 vegetative branches, which do not winter over; the aerial stems, 



* Compare Solereder : Systernatische Anatomie der Dicotyledonen. Stutt- 

 gart, p. 122, 1899. 



