Miscellaneous, 155 



somewhat darker spot in the centre, which is probably a small hol- 

 low space, such as may often be seen in starch. Beside the dark 

 spot in the centre I pbserved layers in the starch of Clinopodium vul- 

 gave, but there were only two in the largest grains. Iodine some- 

 times does not act upon the grains till after the lapse of some minutes, 

 as in Convolvulus arvensis. 



Before I speak of the effect of iodine upon the pores, I must pre- 

 mise, that the pores which are found in the nectaries of many plants 

 have, with but few exceptions, a row of globular grains on the ex- 

 terior margin, distinguished by their size, transparency, and freedom 

 from colour. I found no trace of these grains in the pores of four 

 of the plants I examined last summer, viz. Cakile maritima, Willd., 

 Euphrasia officinalis, L., Statice Limonium, L., Sedum Telephium, L. 

 Iodine had a different effect on the grains of these pores, although 

 in their physical properties they appear to be identical. In seven 

 plants they became blue, and in fourteen brown, of a deep shade, 

 much browner than any other part of the nectary. But whether 

 they became blue or brown, the effect was always a sudden one, and 

 much more rapid than in the case of the grains in the other cells. 

 This may be well observed in Bryonia dioica, in which the rings of 

 the grains in the pores instantaneously appear on the change of 

 colour, which takes place immediately iodine touches the nectary ; 

 whereas the grains in the other cells gradually and slowly assume 

 the blue colour. All these grains, whether they take a blue or brown 

 tint, have no dark spot in the centre nor any trace of layers, but 

 consist of one uninterrupted mass of matter. The seven plants, the 

 grains in the pores of which are coloured blue by iodine, are the fol- 

 lowing : Bryojiia dioica, L., Geranium Robertianum, L., Parnassia pa- 

 lustris, L., Sinapis alba, L., Cnicus lanceolatus, Willd., Scrophularia 

 Balbisii, Hornem., Rubus fruticosus, L. The fourteen plants, the 

 grains of the pores of which iodine colours dark brown, are the fol- 

 lowing : Campanula Trachelium, L., Carlina vulgaris, L., Calendula 

 officinalis, L., Centaurea scabiosa, L. (flower of the disc), Senecio syl- 

 vaticus, L. (flower of the disc), Sonchus arvensis, L., Circcea lutetiana, 

 L., Cichorium Intybus, L., Reseda luteola, L., Samolus Valerandi, L., 

 Helianthus annuus, L. (flower of the disc), Tanacetum vulgar e, L., 

 Hieracium pilosella, L., Helminthia echioides, Gaertn. In all these 

 cases, whether the grains of the pores are coloured blue or brown, 

 the grains of the other cells assume a yellow or brown tint, except 

 Bryonia dioica, in which they become blue, and Sinapis alba, L., in 

 which they take a brownish-blue tint. 



The inquiry now presents itself, what is the granular matter in 

 the nectaries and their pores which is coloured brown by iodine ? 

 I cannot state established facts in reply, but only advance the hypo- 

 thesis, that it is a starch-like substance, from which the sugar of the 

 nectary might be easily produced. I am urged to this conclusion by 

 the following reasons : — 



1st. The brown- tinted grains of the nectaries are in their physical 

 properties, such as form, magnitude, colour and situation, exactly 

 similar to the grains of the eleven or twenty-two plants, — as we include 

 in the number those four plants the grains of which take a blue- 



