IOWA ACADEMY OF SCIENCES. 143 



There is, in the Engelmann herbarium at the Missouri Botan- 

 ical garden, a series of unnamed willows, numbered " 123-146 " 

 inclusive, labeled "M. Jones, Iowa, 1877." These were 

 probably collected in the vicinity of Grinnell, Iowa, by Mar- 

 cus E. Jones, who was once a student there. 



The series includes only our commoner species, viz. S. nigra 

 Marsh., S. amygdaloides Anders., S. alba L. , S, fragilis L., S. 

 fluviatilis Nutt., S. tristis Ait., and S. cordata Muhl. None of 

 these were listed in the body of the paper. 



I. SALIX NIGRA MARSH. 



Salix nigra Marsh. Arb. Am, 139. 1785. 



This is one of our most common willows. It frequents river 

 banks and similar situations, as may be seen by referring to 

 the map. Single trees or clusters of stemsforty to fifty feet 

 in height are not uncommon. The twigs show a great 

 diversity of coloring. The older ones are reddish-brown and 

 usually finely fluted or striated longitudinally. The young 

 twigs are often bright yellowish-green, smooth and shining, 

 gradually becoming reddened by exposure. 



The leaves, when mature, are usually quite characteristic. 

 The typical and most common form is narrowly lanceolate, 

 acuminate, acute or rounded to truncate and even subcordate at 

 the base (and all gradations are to be found on a single twig), 

 quite dark green, with midribs and petioles prominently green- 

 ish-white. Average size four and one-half inches by one-half 

 inch. The variations from this are, as might be expected, in two 

 directions. One is shorter (three inches) and lighter green. 

 The other is longer (five to five and one-half inches), linear- 

 lanceolate, light green, midribs not prominent. This last form 

 was observed in several specimens from Davenport, Muscatine 

 and Mt. Pleasant, although normal forms were also found at 

 those places. Immature specimens of this species and of S. 

 amygdaloides are often very similar in appearance. The just 

 expanding leaves of S. amygdaloides do not always show their 

 characteristic shape and glaucous lower surface and there is 

 little of specific value in the flowers. 



The aments of both sexes vary in length from one to two and 

 one-half inches when mature. The staminate vary in width 

 from three to five lines. The flowering period is about May 1st 

 to May 31st. 



