Robertson — Floivers and Insects. 165 



visitors usually turn upside clown and receive the pollen on 

 the under side. 



On the literature of Slylosanthes see: — 



(1) Kuhn, Einige Beobachtungen iiber Vandellia und den Bliithenpoly- 

 morphisraus. Bot. Zeit. 25:67. 1867.— (2) Chapman, Flora of the Southern 

 United States, 100. 1884. [2d ed.].— (3) Foerste, Botanical notes from 

 Bainbridge, Georgia. I. Bot. Gaz. 18:462. 1893. 



Gymnocladus canadensis Lam. — G. dioicus (L. ) Koch. — 

 The Coffee-tree is a large tree, growing in creek bottoms and 

 blooming from May 7 to June 1. The flowers are regular, 

 are arranged in panicles and are said to be dioecious or 

 polygamous. The calyx-tube is about 10 mm. long, with five 

 equal lobes, and with five petals and ten stamens inserted 

 near the throat. The stamens are somewhat exserted, five of 

 them being longer than the others. The anthers are introrse, 

 form a circle about the mouth of the calyx-tube and serve to 

 narrow the entrance. Nectar is secreted by the inner wall of 

 the tube. 



An adaptation to bumble-bees is indicated. The following 

 visitors were noted on May 10 : — 



Apidae: (1) Bombus americanorum F. ?, s., freq.; (2) B. virginicus 

 Oliv. ?, s. & c. p.; (3) Synhalonia frater Cr. tf, s. 

 Papilionidae: (4) Papilio troilus L., s. 

 Trochilidae: (5) Trochilus colubris L., s. 



Spiraea L. — According to Miiller (4), S. uhnaria is devoid 

 of nectar and is homogamous, though Axell (2) calls it proter- 

 androus. Cross and self-pollination may be effected by in- 

 sects, or, in their absence, spontaneous self-pollination or 

 geitonogamy may occur. According to Schulz (18), this 

 species and 8. filipendula are andro-monoecious. Kernel* 

 (19) calls the scent of S. ulmaria benzoloid. 



S, filipendula is also homogamous and devoid of nectar, 

 according to Miiller. Insects effect cross-pollination ; in their 

 absence, spontaneous self-pollination takes place. 



On account of their abundant nectar and pollen and their 

 proterogynous condition, S. salicifolia, ulmifolia and sorbi- 

 folia are abundantly cross-pollinated by insects. When these 

 fail, there may be spontaneous self-pollination (Miiller). In 



