DRY GRASSLAND OF A MOUNTAIN PARK 267 



Androsace piiberidenta, Collinsia parviflora, Orthocarpus luteus. 

 Of these short-lived species most are rare or infrequent; only 

 Orthocarpus luteus is at all common. 



UNDERGROUND PARTS 



A study of the underground parts of the 36 most important 

 plants (marked with an asterisk in the systematic Hst at the 

 close of the article) showed the folloTNdng features: 



per cent 



Shallow-rooted 70 



Deep-rooted 30 



Stolons present 14 



Rhizomes present 33 



Rhizomes absent; often a much-branched caudex 53 



All the grasses and sedges are shallow^ rooted and in addition 

 the following: Eriogonum wnhellatum, Cerastium occidentale, 

 Sedum stenopetalum, Mertensia bakeri, Orthocarpus luteus, Cam- 

 panula petiolata, Achillaea lanulosa, Antennaria (4 spp,), Arte- 

 misia frigida. The . sedges and about one-half of the grasses 

 spread by rhizomes; the other perennials by innovations at the 

 stem base. Of the dicotyledons in the list only the following- 

 have tiTie rhizomes : Cofnandra pallida, Cerastium occidentale. Cam- 

 panula petiolata, Achillaea lanulosa, Antennaria anaphaloides . 



H>^erxerophytic areas have, perhaps, the greater number of 

 deep-rooted plants, as Potentilla concinna, P. hippiana, P. 

 Pennsylvania strigosa, Erigeron multifidus, Chrysopsis villosa. 

 But in these same situations the shallow-rooted Selaginella 

 densa and Carex stenophylla occupy much of the ground. Both 

 types of plants have their advantages. Shallow-rooted forms 

 make use of the moisture from light showers which are frequent 

 in the growing season, while deep-rooted plants are able to draw 

 upon the soil water of lower levels. 



LIST OF VASCULAR PLANTS OF THE DRY GRASSLAND 



The following list includes all vascular plants recognized 

 within the dry grassland of Boulder Park with the exception of a 

 few species occasional along roads or elsewhere and evidently 



