CHAPTER XVI 



flourish. When several dry years come in succession, it is interesting 

 to watch the struggle for supremacy between the two weeds; for a 

 time the Ainsinckia,whose qualifications are set forth in the Supple- 

 ment to Chapter IX, take the lead, but ultimately the perennial plant 

 crowds the annual to the wall. 



Of the minor annual weeds of winter and spring time, Orthocarpus 

 purpurascens, illustrated in Fig. 54, the well known tidy-tips, and 

 Phacelia tanacetifolia, Fig. 45, and its near kin, are simply vigorous 

 natives that do not at once succumb to cultivation. The two former 

 are mildly troublesome in grain fields, the last is common along way- 

 sides and in waste places generally. The Calandrinias, Chapter IX, 

 Supplement, are short-lived, but their fleshy leaves and numerous 

 seeds are elements of strength. Our native nettles flourish all the 

 year if left in their chosen habitats. The dodder is sometimes very 

 troublesome in alfalfa fields, Tropidocarpum gracile, Hook., is a 

 yellow flowered Crucifer rather persistent in irrigated loamy soils, 

 especially in the desert. Another Crucifer, the shepherd's-purse 

 (Chapter IX), makes itself at home in California as everywhere else 

 in the world, but can hardly be termed troublesome. Of introduced 

 weeds of the pink family, Silene gallica, Linn., is very prolific in 

 some warm sandy soils; it is nearly as viscid as its cousin ,5*. laciniata 

 of Chapter XV, and has short, one-sided clusters of white or pinkish 

 flowers of medium size; the spurry, Spergula arvensis, requires more 

 moisture, and is even more local; the chickweed, Stellaria media, as 

 noted in Chapter IX, is widely distributed and persists the year 

 round. The pimpernel, noted in Chapter XIV, Supplement, is an- 

 other not very offensive weed that blooms and fruits the year round. 



Many of the summer and autumn weeds have been already con- 

 sidered; the milkweed, Asclepias, in the previous chapter ; Tricho- 

 stema and Bremocarpus,in Chapter V and elsewhere ; and, in the Sup- 

 plement to Chapter XII, the various weeds belonging to the Com- 

 positae, the sunflower, tar- wetds, ragweeds (Ambrosia), fleabane 

 (Erigeron), Mayweed (Anthetnis cotula), cockle-bur (Xanthium), 

 sow-thistle (Sonchus), and Spanish-needle (Bidens.) The sow-thistle 

 is illustrated in the Reader ; the cockle-bur and Spanish-needle, like 

 the hoarhound, are too notorious to need illustration ; the Mayweed 

 seems to be rapidly gaining ground in the north; in the south a 

 nearly related native plant, Matricaria discoidea, DC., is more aggres- 

 sive, but neither is yet troublesome. The yellow star thistle, Ctn- 

 taurea melitensis, Linn., is a pest that perhaps ranks next to mustard 

 and wild barley in the north, but in the south it is limited to pasture 

 lands. The two species of Euphorbia, E. albomarginata and E. 



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