Mr. Dickie on the Reproductive Organs of the Lichens. 165 



Choquier. It is entirely enveloped, the height increases ra- 

 pidly, its form is in consequence very discoid, and this di- 

 stinguishes it from A, Diadema, with which it must never be 

 confounded. The shell is extremely thin and very finely 

 striated and plicated. The folds, as far as I have been able 

 to observe, present no change in their direction. The lobes 

 agree in all their characters, as has been already remarked, 

 with those of the two preceding species. It remains gene- 

 rally very small, being seldom more than three-fourths of an 

 inch in diameter. 



XVIII — Remarks on the Reproductive Organs of the Lichens, 

 By George Dickie, Esq., A.L.S., Lecturer on Botany at 

 Aberdeen. 



Starch seems to be a product of almost universal occurrence 

 in the vegetable kingdom ; it is foimd in stems, roots, &c. ; and 

 in the parts of fructification of many plants, it is abundant, and 

 appears to serve a very important purpose. It is plentiful in 

 the disk of the almond, and Dunal has detected it in the disks 

 of certain species of Arum ; and it is supposed to undergo a 

 certain change in order to render it fit to afford nourishment to 

 the pollen and young ovules. Its presence in the ripe seed is 

 well known, and its use during germination has been fully 

 established. But starch is not confined to what are called the 

 higher tribes of plants ; it is also found in some which are 

 generally allowed to stand low in the scale of vegetables. In 

 ' Mag. Zoology and Botany,^ vol. i. p. 382. I have stated that 

 it occurs in the nucules of Chara vulgaris, and in the bodies, 

 formerly called capsules, of Pihdaria globulifera, in both of 

 which it is also found along with a matter having all the pro- 

 perties of a fixed oil ; it also occurs in those pyriform bodies 

 which are found in the axillae of the leaves of certain species of 

 Jungermannia, ^ Mag. Zool. and Bot.,' vol. i. p. 592. So that 

 the bodies in the capsules of Pilularia are grains of starch and 

 not sporules, and the contents of the anthers (of some authors) 

 of Jungermannia consist also of the same substance. The 

 bodies, which are found in the tubes (transversely undulated 



