240 SHORT NOTES. 



^STiYATioN IX AsiMTNA. — The aestiviition was formerly thought 

 to be valvate in all Anonacece. In the ** Genera Am. Bor. 

 lUustrata," vol. i., 1848, it is mentioned that the petals of each set 

 are more or less imbricated in Asimina, as also in some other genera. 

 The petals enlarge so much before and during expansion that the 

 proper aestivation needs to be determined in young flower-buds. A 

 subsequent examination of these, in A. triloba, showed that there 

 was hardly any overlapping in an early state. Accordingly, in the 

 later editions of my Manual, no exception to the ordinal character, 

 ** valvate in the bud," is alluded to. In the '' Genera Plantarum," 

 Bentham and Hooker distinguish their two tribes, Wvariece and 

 UnonecB by the aestivation of the petals — more or less imbricated in 

 the former, valvate in the latter, to which they refer Asimina. Last 

 spring I had an opportunity to examine, on the living plants and 

 flower-buds of A. grandijlora, the species in which the exterior petals 

 are most accrescent, and the interior perhaps least so, the one which 

 most resembles Uvaria in the appearance of the blossoms. The sepals 

 appear to be truly valvate. The outer petals are decidedly imbricated, 

 their tips well overlapping in the order 1,2, 3, in the early bud, and 

 remaining so during the great enlargement ; but down the sides they 

 do not overlap, nor are their bases contiguous. The inner petals are 

 remote in bud : moderately accrescent, they remain proportionally 

 small, and from first to last do not come into contact, the margins 

 above the middle becoming revolute in anthesis, while the base grows 

 more and more deeply concave and papillose-ridged. This portion is 

 frequented by thrips, or such-like insects, as also is the mass of 

 stamens as soon as the anthers open. The flowers are proterogynous, 

 the stigmas being early in good condition, the anthers discharging 

 pollen only when nearly ready to shrivel and fall. On examining 

 good fresh flower-buds of A. triloha, in May, I find that the sepals are 

 truly valvate at first, but separate more or less as the bud swells. 

 The exterior petals, a little distant at their bases, very slightly over- 

 lap as they meet at the summit, while just below the margins become 

 a little revolute. The interior petals are similar, but rather more 

 distant at base, and rather less obscurely, yet very slightly, over- 

 lapping at the very tips. As they increase in size they slightly assume 

 the imbricated position which becomes conspicuous in the outer petals. 

 I conclude that the tribe UnonecB cannot be distinguished from the 

 Uvariece, at least upon the characters assigned, and that the one kind 

 of aestivation passes by gradations into the other. — A. G. in " Silli- 

 man's Journal," July, 1875. 



The Lichen Question. — Dr. Xoerber, one of the first Lichenologists 

 of Europe, in his ''Zur Abwehr der Shwendener-Bornet'schen 

 Elechten-theorie " (Breslau, 1874), has cast the weight of his 

 authority against the theory, which has received considerable 

 currency, that Lichens are a compound of an Alga (the 

 gonidia) and a Fungus (the hyphas). He maintains, first, that the 

 *'nicht-gonimische," i.e., the hyphae, and the lichens themselves are 

 not Fungi, citing, in support of this proposition, the known chemical 

 and other diflFerences between the two, and the fact that many lichens 

 are altogether destitute of hyphae. He is curious to know how, on the 

 theory of Schwendener, the formation of a Ihallus from the copulation 



