T. Holm — North American Species of Stellar ia. 321 



thus, die down to the ground at the end of the first season. 

 As mentioned above, this species possesses a rhizome which 

 shows a much higher development than that of other American 

 representatives of the genus. Our figures 4-6 illustrate the 

 external structure of the rhizome. It is horizontally creeping ; 

 the internodes are partly swollen and tuberous ; they root 

 freely, especially at the nodes. The leaves of the rhizome are 

 opposite, scale-like, and membranaceous ; they support buds, of 

 which those that are located near the apex of the rhizome de- 

 velop into aerial, floral shoots; the others stay dormant. It is 

 a structure which is very common, and characteristic of many, 

 very different genera, but it seems to be very rare within the 

 Alsinece, and perhaps within the CaryqphyllacecB in general. 

 If we examine the internal structure, we notice the same struc- 

 tural peculiarities which we are used to find in rhizomes that 

 store nutritive matters. In the slender portions of the inter- 

 nodes the epidermis is thin walled, and no hypoderm is devel- 

 oped ; the cortical parenchyma consists of about five layers, and 

 does not contain starch; a few layers of very thinwalled cork, 

 which has originated from the innermost stratum of the cortex, 

 surround a pericycle of a closed sheath of mostly six layers of 

 moderately thickened collenchymatic tissue; but there is no en- 

 dodermis. We find in the stele five separate, collateral mestome- 

 strands, w x hich contain cambium. There is no interfascicular 

 cambium; thus the mestome-strands are located in the periphery 

 of a broad central parenchyma, w r hich contains druids of calcium 

 oxalate, and large deposits of starch, the starch-grains being 

 of equal size, and quite large. 



A corresponding structure is to be observed in the swollen 

 portion of the internodes, with the exception of the pith being 

 much broader, and the mestome-strands, the secondary, having 

 a much longer radius, when viewed in cross-sections. The 

 structure of the primordial mestome is as described above, but 

 the secondary haclrome appears here as a long and very narrow 

 line of vessels in each strand ; the pith is hollow in the center. 

 The secondary formations are, thus, limited to the stele, and 

 the nutritive matters are deposited in the pith, but not in the 

 cortex. 



In bringing these facts together it is readily to be seen, that 

 our species of Stellaria are not so very uniformly developed in 

 regard to the means by which the hibernation and vegetative 

 reproduction is effected. The three biological types which we 

 have suggested are well marked, and might, with some benefit, 

 be included in the specific diagnoses. But otherwise the mor- 

 phological structure is very uniform in this genus, and we 

 might at the same time take the opportunity to make a correc- 

 tion in regard to the inflorescence, as described in the Synop- 



