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50 MISSOURI BOTANICAL GARDEN. 



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Synopsis. 



Group I. — Secondaries regular. 



1. S. alba, L. — Primaries numerous, close, straight, 

 high-ascending, mostly extending to margin without divid- 

 ing or branching, forming but a few acute loops towards the 

 apex. Costals intervening, seldom more than one well- 

 developed, often none. Secondaries close, straight, even, 

 conspicuously regular with the exception of a rather fre- 

 quent forking or imitation of the letter Y. Tertiaries 

 very irregular, uneven, and, as usually observed, forming 

 incomplete meshes owing to partial early obliteration. 

 Except in very young leaves the impression made is there- 

 fore of quite regular veining throughout. It is the typical 

 leaf of regularity. — Plate 1, fig. 1. 



Illustration is from var. vitettina, Koch. The leaves 

 of the typical form of S. alba examined showed greater 

 irregularity. 



2. S. fragilis, L. — With slight modification the 

 description of alba applies to this throughout. The looping 

 is usually more decided, the loops less acute, and there is 

 more curving of the secondaries, and especially of the costals. 

 There is perhaps greater disposition to irregularity. The 

 veins of both are brilliant as they traverse the dense green 

 of the leaf. Of all the species in my list there is, in this 

 pair, the nearest approach to sameness. Since, however, 

 the external characters are different, no difficulty will arise 

 in distinguishing them from each other. /S. lucida, also, 

 has a near resemblance to both. — Plate 1, fig. 2. 



Illustration from vicinity (cult.). 



3. S. lucida, Muhl. — Primaries close, regular, curved- 

 ascending, forming towards the apex roundish not very 

 pronounced loops; intervening costals seldom more than 

 one, or none. Secondaries regular, close, curving, often 

 forking or having the Y shape. Tertiaries form irreg- 



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