19*2 
ORGANOGRAPHY. 
BOOK I. 
pollen is either too much or too little transparent to show the 
apertures in its sides, he finds a solution of iodine in weak 
spirits of wine extremely useful. — 2. Mohl, Sur la Structure et 
les Formes des Grains de Pollen : translated from the German in 
the Annales des Sciences, n. s., III. 148. — And, 3., to Fritzsche, 
Veber der Pollen : 4to, St. Petersburgh, 1837, with thirteen 
coloured plates. In this last excellent work all the refine- 
ments of optical instruments and chemical manipulation have 
been employed in the investigation of the subject. 
10. Of the Disk. 
By this' term are meant certain bodies or projections, situ- 
ated between the base of the stamens and the base of the 
ovary, but forming part with neither ; they are referred by 
the school of Linnaeus, along with other things, to nectarium : 
Link calls them sarcoma and perigynium ; and Turpin, phy- 
costemones. The most common form is that of a fleshy ring, 
either entire or variously lobed, surrounding the base of the 
ovary (Plate V. fig. 4. e, 8. d.) as in Lamium, Cobaea, Gra- 
tiola, Orobanche, &c. ; in Gesneraceae and Proteaceae the disk 
consists of fleshy bodies of a conical figure, which are 
usually called glandulce liypoyynce. It occasionally assumes 
the appearance of a cup, named by De Candolle, in Paeonias 
and Aconites, lepisma, a bad term, for which it is better to say 
discus cyathiformis. In flowers with an inferior ovary (Plate V. 
fig. 9. c, 7. c) the disk necessarily ceases to be hypogynous, and 
generally also to appear in the form of scales. In Compositae 
it is a fleshy solid body, interposed between the top of the 
ovary and the base of the style ; and has given rise, when 
much enlarged, to the unfounded belief in the existence of 
a superior ovary in that order, as in Tarchonanthus. In 
Apiaceae it is dilated, and covers the whole summit of the 
ovary, adhering firmly to the base of the styles; by Hoffmann 
it is then called stylopodium, a word which is seldom used. 
It is an opinion which daily gains ground, that the disk is 
really only a rudimentary state of the stamens ; and it is 
thought that proofs of the correctness of this hypothesis are 
to be found in the frequent separation of the cyathiform disk 
