CRITERIA. 169 



every species, there is an overlapping in the totals, so that this character again possesses 

 no specific value. It is useful, however, in distinguishing divisions of those species in 

 which the alinement of the rows has been lost and where in consequence the total varies 

 by units rather than by fives. This is brought out in table 22 (p. 207), where, for example, 

 it will be noted that the number for the asper-vulcanicus-monocephalus group of subspecies 

 of C. parryi runs from 8 to 13, with an average of 10.4, whereas in the howardi-attenuatiis- 

 nevadensis group it runs from 11 to 21, with an average of about 13. 



Inflorescence. — The heads are borne in cymes, racemes, spikes, or panicles. The cyme 

 is by far the most common type and occurs with some modifications almost throughout 

 the Typici and Pulchelli and in C. nauseosus. In the anomalous C. gramineus the 

 inflorescence is apparently a much reduced raceme, while the racemose tj^pe is char- 

 acteristic for C. parryi. In this last, however, the peduncles are sometimes so branched 

 that small panicles are the result. This condition gives an inflorescence simulating 

 the compound cymes sometimes seen in C. nauseosus. In the Punctati the inflorescence 

 is essentially spicate in one species, truly paniculate in the other. Observations in the 

 field have demonstrated that the size and density of the inflorescence are too variable to 

 be of much taxonomic significance. Although conspicuous in their extremes, the forms 

 resulting from such considerations can not be satisfactorily treated even as subspecies. 



Leaves. — The leaves are always alternate (partly fascicled in one species) and entire. 

 The remaining characters, such as size, shape, and texture, are seldom of diagnostic value 

 as far as species are concerned. Terete leaves occur only in the Punctati; in one species 

 (gramineus) they are exceptionally wide and without intraspecific gradations; and in 

 one other case the shape is useful as a specific distinction (between pulchellus and depres- 

 sus), but these leaf-characters are always used in connection with others and aside 

 from the instances here mentioned, the foliage furnishes criteria useful only when dealing 

 with subspecies. A consistent attempt has been made to utilize the number of nerves 

 and their prominence, but without much success. It is only in comparing species which 

 are rather clearly separated on other characters that such features can be called into use 

 and then only as additional evidence. Much has been made heretofore of the number of 

 veins as a specific character in segregations from C viscidiflorus, but here the number 

 depends largely upon the width of the leaf. There is one plain midvein and usually two 

 others that start from the base but are soon lost or become invisible. Very often a plant 

 will seem to have only 1-veined leaves, but on close examination a few leaves with 2 or 

 3 veins will be found (for example, C. parryi monocephalus, Univ. Calif. Herb. 76001 ; 

 C. parryi nevadensis, Univ. Calif. Herb. 31167; C. viscidiflorus typicus, Univ. Calif. 

 Herb. 51644, 203178). 



Stem and bark. — To one accustomed to handling the plants in the field, there is a 

 decided difference in the stems of certain species, although the characters are not easily 

 described. Thus, in the Typici, Pulchelli, and Punctati the twigs are very brittle, whereas 

 in the Nauseosi they are much more flexible. The bark of the year-old twigs is usually 

 white in the Pulchelli and Typici, green or brownish, although sometimes covered with a 

 white pubescence, in the Nauseosi. The striation of the younger stems is often of diag- 

 nostic value. In the last-mentioned section, however, this is likely to depend upon the 

 nature of the hairy covering, which may be either loose, thus masking the striae, or 

 closely compacted and thus exposing them. The older bark of the main trunks affords 

 specific characters, but not of such a nature as to be usable in keys. The color of the 

 plant as a whole, whether due to bark, foliage, or only pubescence, has been made use of 

 in specific descriptions, but this is too variable and elusive to be of value in dealing with 

 any category above that of subspecies. 



Roots. — It is quite probable that specific distinctions could be derived from the system 

 of root-branching if this were well understood. The only root studies made were in the 



