OBSERVATIO>'S ON SOME OF THE PLANTS EXHIBITED. 455 



OBSERVATIONS ON SOME OF THE PLANTS EXHIBITED. 

 By Rev. Prof. G. Henslow, M.A., V.M.H., &c. 



[July 30, 1001.] 



Heliotrope. — The European species, H. europmim, was long known 

 by this name, which means " sun-turning." The popular idea of the 

 Middle Ages was that it " turned to the sun " ; but Gerarde, who pub- 

 lished his Herball " in 1597, observes that the real meaning was that it 

 flowered about the time of the summer solstice, when the sun turned in 

 its course. Another name was Solsequium, from sol (the sun) and 

 \ sequor (to foUow), but several other plants acquired this name, especially 

 among Composites. 



Another peculiarity in the Heliotrope resides in the structure of the 

 pistil ; for, excepting the Periwinkle of a different family, it is the only 

 kno^\Tl plant which has the stigma heloiu and not at the apex of the style. 

 It forms, in fact, a stigmatic ring round it. The explanation of this 

 unique pecuHarity is not known. 



Celosia pyramidalis. — Fine specimens in Mr. Jones's collection 

 showed the primitive form from which the Cockscomb has arisen. It is 

 remarkable for the numerous branchlets covered with purple bracts. It 

 was thought that the " fasciated " stem, known as the Cockscomb, was 

 due to the fusion of the numerous floral branchlets into the well-known 

 flat massive structure. Such an interpretation would not be correct ; for 

 when two branches or organs are fused together, the epidermis of each 

 is suppressed. In the Cockscomb the only elements to represent the 

 branches are the internal fibro- vase alar cords which are present in a 

 single flattened stem, surrounded or enveloped in a common epidermis.* 



Lobelia cardinalis. — This old-fashioned flower was selected a^ 

 illustrating the probable origin of the great family of Compositce. The 

 character of having the florets in heads, it was pointed out, is not the 

 only one ; as the species of Scabious, of which specimens were exhibited, 

 have their inflorescence similarly in heads, but they do not belong to this 

 family. The most distinguishing feature is that the anthers are united, 

 forming a cylinder. This is also the case with Lobelia. In both this genus 

 and in the Compositce the method of insect fertilisation is the same, in 

 that the style continues to elongate till it has thrust the closed stigmas 

 through the anther- cylinder. In so doing a tuft of hairs on the style 

 sweeps out the pollen. It is not tiU this is effected that the two style- 

 arms with their stigmatiferous surfaces open and become spread out. If 

 a flower of Lobelia be compared with a disc-floret of Centaurca, the 

 similarity will be at once seen. It is consequently suspected that Lobelia 

 represents the line of evolution which issued in the great family Com- 

 pos it ce. 



Delphiniums, Single and Double. — Larkspurs are characterised 



* The reader is referred to the author's previous paper on " Fusciation and 

 Allied Phenomena " at page 155. 



