244 SENECIO VULGARIS. 



The leaves appear to be destitute of raphides, but the cells 

 apparently contain large quantities of very minute starch-grains. 

 In some of the leaves I have also detected some large discs of a 

 substance which I take to be Inuline (Fig. 6, under polarised light). 



Inuline is closely related to starch and sugar, and, according to 

 Sachs, is very abundant in the cell-sap of the Compositae, and may 

 be readily developed by the application of alcohol, when it will be 

 detected in large masses of a spherical crystalline structure, which 

 under polarised light appear very similar to the crystals of Oxalu- 

 rate of Ammonia, showing a distinct cross with its point of diver- 

 gence exactly in the centre of each sphere. As in my experiments 

 all the leaf-sections, as well as the whole leaves, have been pre- 

 pared in alcohol, I venture to suggest that these beautiful polar- 

 ising discs are most probably inuline. 



The floral structure of the Groundsel must now claim our 

 attention. The flowers are in clusters surrounding the stem of the 

 plant, and each composite head is situated upon a floral stem. 

 To an ordinary observer there is nothing attractive in the small 

 green capsules with bulging bases and black, pointed calyx-scales ; 

 and were it not for the bright yellow adornment above them, 

 tipping as with richest gold the long green caskets, many 

 persons would scarcely recognise any flowers at all. But within 

 them lies a rich and varied store of creative skill and adaptation, 

 and we are compelled to use lens, needle, and scalpel to assist 

 us in the elucidation. 



The " involucre," or green cup, which encloses all the florets is 

 composed of sixteen or seventeen sepals or bracts. The involucre 

 is double, and has smaller bracts at its base ; the longer bracts 

 tightly enclose the " capitulum," or head of florets attached to the 

 receptacle, and on the seeds becoming mature they unclasp and 

 fall downwards below the receptacle, but they still remain attached. 

 By mounting several of them, both stained and unstained, we dis- 

 cover that the apex of each, which when in growth is almost black 

 in colour, shows a pretty fringe of membrane when examined 

 under polarised light (Fig. 7). This involucre is the calyx des- 

 cribed by Withering and all old botanists. 



, The calyx proper is that which surrounds each floret, and in 

 the case of the Groundsel, Dandelion, and Thistle, is really the 



