ROBINSON. — ALOMIA, AGERATUM, AND OXYLOBUS. 455 



and technical characters, and several are scarcely to be separated 

 from Trichogonia except by their slightly shorter and thicker pappus- 

 bristles. Their satisfactory generic disposition must await further 

 study, for which there is no adequate material as yet available in the 

 North American herbaria. 



The other two elements traditionally included in Agcrahim, namely, 

 the true Ageratums with pappus of distinct scales, and Coclcstina Cass. 

 with cuplike or crownlike pappus, are groups of very close affinity, 

 by no means sharply separable. It is believed that they are best 

 treated merely as sections of the genus Agcratum. 



The writer has not had many opportiniities to follow up the various 

 forms of Agcratum which have received horticultural names. So far 

 as seen these have proved merely cultural improvements of the com- 

 mon annuals, A. conyzoides L. and especially A. Houstonianum Mill. 

 A. rubens Viviani, early described from cultivated material, has never 

 been recognized. A. Lasseauxii Carr., to judge from a supposably 

 authentic specimen in the Gray Herbarium, is clearly a species of 

 Eupatorium. A. conspicuum Hort. is generally believed to have been 

 Eupatormm glechonophyllum Less. Ageratum Wendlandii of Vilmorin's 

 Fleurs de pleine terre, Suppl. 2 (1884), Avith uncharacteristic figure 

 and mere horticultural description, was presumably founded on the 

 same plant as the one to which Schultz-Bipontinus applied the manu- 

 script name Phalacraca Wendlandii, later published in synonymy by 

 Klatt. If this is the case Vilmorin's plant was the one described else- 

 where in this paper as Alomia Wendlandii and came from the uplands 

 of southern central Mexico. It would seem probable that both Agcra- 

 tum and Alomia would repay further horticultural attention, there 

 being seAeral other species quite as promising as those already brought 

 into cultivation. 



AGERATUM L. (Nomen ab antiquis et graece et latinice ad 

 plantam aliquem non viescentem non certe cognitam fortasse ut dici- 

 tur ^Ichillcam applicatum.) — Capitula homogama tul)uliflora. In- 

 volucrum plerumque campanulatum rariter turbinato-subc\'Jindratum 

 vel hemisphaericum, squamis angustis longitudine subaequalibus 2-3- 

 seriatim imbricatis (cum vel absque squamulis 1-3 extimis multo 

 brevioribus) plerisque lanceolato-linearibus acutis vel attenuatis 

 saepius 2(l-4)-costatis. Receptaculum planum \e\ convexum vel 

 conicum nudum vel paleiferum. Corolla 5-dentata limbum versus 

 saepius caerulea vel purpurea xel alba rarius rosea, tubo proprio 

 superne sensim in fauces subcylindratas plus minusAe ampliato. 



