CUPULIFERAE 379 



Kemer, loc. cit. ; Schulz, Ber. D. bot. Ges., Berlin, x, 1892; von Wettstein, Verb. 

 Zool.-Bot. Ges., Wien, xl, 1890, pp. 68-79.) MacLeod says that the S catkins of 

 this species are larger than the $, the latter possessing a more flexible axis than the 

 former. Schulz observed occasional hermaphrodite flowers, and von Wettstein found 

 entirely male and entirely female specimens. 



i 2572. B. pubescens Ehrh. (= B. alba Z., according to the Index Kewensis). - 

 As the preceding species. 



2573. B. nana L. (Abromeit, ' Bot. Ergeb. von Drygalski's Gronlandsexped.,' 

 'p. 77 ; Andersson u. Hesselman, * Bidrag till Kanned. om Spetsbergens o. Beeren 

 Eil. Karlvaxtflora,* p. 667.) Vanhoffen {cf. Abromeit, loc. cit.) describes the dwarf 

 oirch as being among the less fragrant plants of Greenland. In Spitzbergen 

 '23. 7. '98) it was found growing, and bearing numerous J and 5 catkins, in a low 

 sheltered branch of Advent Bay Valley. A specimen collected by Bjorling (26. 7. '90) 

 possessed well-developed but seedless fruits {cf. Andersson and Hesselman, loc. cit.). 



807. Alnus L. 

 Flowers anemophilous ; monoecious ; sometimes hermaphrodite. 



2574. A. glutinosa Medic. (Bail, Bot. Ztg., Leipzig, xxviii, 1870; Schulz, 

 ^r. D. bot. Ges., Berlin, x, 1892; Kemer, loc. cit.; Kirchner, ' Neue Beob.'; 

 MacLeod, op. cit., pp. 12 1-3.) Bail and Schulz state that hermaphrodite flowers 

 ire not rare in this species ; they are at least much more frequent than in Betula. 

 kirchner describes the stocks as protandrous, the stigmas not maturing until the 

 ) flowers have withered. Kemer, however, says that they are protogynous, the 

 _> flowers maturing before the J. MacLeod states that the J and 5 catkins mature 

 imultaneously, and appear before the leaves. The S catkin possesses a long flexibl 

 xis, which can be set in motion by the wind ; this bears the flowers in groups of 

 hree. The 5 catkins are much smaller, the flowers being arranged in pairs. 

 Vamstorf describes the pollen-grains as pale yellow in colour, decahedral with blunt 

 ngles, 31 /I in diameter, smooth, with five germinating processes. 



2575. A. viridis DC. Kemer states that the j flowers of this species mature 

 .-5 days earlier than the J ones on the same plant. 



cm. ORDER SALICINEAE RICH. 



808. Salix L. 



Literature. Sprengel, ' Entd. Geh.,' pp. 437-8 ; Herm. MuUer, * Fertilisation,' 

 p. 524-6; Kemer, 'Nat. Hist. PI.,' Eng. Ed. i, II, pp. 313-14; MacLeod, Bot. 

 aarb. Dodonaea, Ghent, vi, 1894, pp. 128-9; Knuth, 'Grundriss d. Bliitenbiol.' ; 

 pEeinricher, Sitz.-Ber. Ak. Wiss., Wien, Ixxxvii, 1883. 



Flowers entomophilous ; dioecious ; with half-concealed nectar. The mechanism 



f willows is the simplest found among insect-pollinated forms. Although the flowers 



i re insignificant they are rendered conspicuous by being aggregated into catkins, 



specially as these generally appear before the leaves unfold. Both the more con- 



picuous S flowers (which are therefore the first to be visited by insects), and the ?, 



