Miscclla neons. 487 



fertile it is fair to assume tliat it must be arranged for sclf-pnilina- 

 tion. In Asclepiadacea;, with the large majority of the (lowers 

 barren, we may theoretically assume inflect agency, — with many 

 abundantly fertile Apocynaceoe we may assume self-fertilization. 



I have already shown that the Madagascar periwinkle, Vinca 

 rosea, with every flower fertile in American gardens, is a self- 

 fertilizer. Another of the same order, Amsonia Taherncemoatana 

 (the form known as A. saUcifolia, Pursh), is abundantly fertile. I 

 watched the flowers this season, satisfied that they would be found 

 arranged for self-pollination. The plants proved, as usual, abuu- 

 dantly fertile. On one ])aniclo there were twenty-nine pairs of 

 fi)llieles that matured ; there were many others that had been 

 evidently fertilized, but failed to reach maturity through lack of 

 nutrition. 



Showy as the blue flowers are, and we might suppose, in view of 

 prevailing speculations, made so in order to be attractive to insects, 

 the arrangements are such that no insect, not even the ubl(iuitous 

 thrips, can gain entrance to the nectary. The mouth of the tube is 

 BO densely matted with hair that Favx clansa is the term used in 

 the description of the species by Latin authors. If a pollen-clothed 

 tongue were thrust through the mass it would be thoroughly 

 cleaned, and in like manner the flower's own pollen would bo 

 ])rushed back when the insect withdrew its tongue. But a greater 

 difficulty presents itself. The capitate stigma with its surrounding 

 rim completely fills the upper portion of the tube. There is no 

 space for an insect's tongue to get past the stigma. But even could 

 this rubicon be passed, a dense mass of hair presses close against 

 the style, and the most powerful insect known to the writer could 

 hardly force a passage. The entrance of insects is completely 

 blocked. To provide for pollination the anthers curve over and 

 rest on the stigma, and the pollen on ejection from the anthers can 

 do no more than cover the stigma. 



In many plants which have flowers that are generally fertilized 

 by their own pollen the arrangements will often permit of polliua- 

 tion from some other ; but in the case of this Amsonia nothing but 

 self-pollination is possible. 



To those who may not have flowers for comparison the figure of 

 this plant in ' Botanical Begister,' pi. 151, will aid in making some 

 of the above-noted points clear. — Froc. Acad. Nat. Sci. Philud. 

 March 29, 1892, p. 162. 



