258 



ANGIOSPERMAE—DICOTYLEDONES 



5 mm. by 2 mm. broad, and 3-4 mm. long. Vestigial stamens surround the hair- 

 covered ovary, but their anthers do not dehisce. 

 Visitors. — Kirchner observed the honey-bee. 



635. A. rubntm L. — The flower mechanism of this species, which is also 

 native to North America, essentially resembles that of A. dasycarpum (Kirchner, 

 op. cit.). 



636. A. tataricum L. — Francke states that this species, indigenous to Carniola 

 and Russia, bears male flowers with vestigial ovaries, and female flowers with vestigial 

 stamens. The hermaphrodite flowers are crossed with pollen from male flowers, 

 since their own matures late. 



XXXII. ORDER ANACARDIACEAE Lindl. 



192. Rhus Tourn. 



Hermaphrodite or unisexual greenish flowers, with exposed nectar secreted 

 by the receptacle. The hermaphrodite flowers are homogamous or often pro- 

 tandrous (Darwin). 



Fig. 80. Rhus Coiinus, L. (after Herm. Mullerl. (i) A purely male flower. (2) A hermaphrodite 

 flower. (3) A purely female flower, s, sepals; p, petals; a, anthers; J/, stigmas ; ;;, nectary. 



637. R. Cotinus L. (Herm. Miiller, 'Fertilisation,' pp. 166-7; Schulz, 

 ^ Beitrage,' II, pp. 62-4.) — In this species, according to the observations which 

 Hermann Miiller made on garden plants, numerous intermediate stages between 

 purely male, hermaphrodite, and purely female flowers are present on the same 

 stock. The purely male flowers, being the largest, and opening the widest, are 

 the most conspicuous. The female ones are the smallest, and open least, so that 

 they are the most inconspicuous. The flowers are consequently visited in the 

 order best adapted to secure cross-pollination. Schulz, who studied wild plants 

 in the South Tyrol, also observed three distinct forms diff"ering in the development 

 of stamens and carpels. The plants, however, were dioecious, like the cultivated 

 varieties at Halle. Schulz states that there are two series of female flowers, one 

 (diameter 3^-4 mm.) possessing anthers shaped like those of the male flowers, 

 but with abnormal pollen-grains. The stamens of the second form (diameter 

 Z~Z\ nim.), on the other hand, are quite vestigial. The diameter of the male 

 flowers is 5-6 mm. According to Schulz, the distribution of the flowers is dioecious, 

 or more rarely monoecious. In all cases there is a secreting yellow or orange- 



