232 AN GIOSPERM AE— DICOTYLEDON ES 



opened so wide that a humble-bee in search of nectar can strike against the anther- 

 processes, by which means the powdery pollen is showered down. Cross-pollination 

 by insect-visits is therefore ensured. 



LXXV. ORDER OROBANCHACEAE RICH. 



677. Orobanche L. 



Homogamous, more rarely protogynous bee flowers, sometimes with nectar 

 secreted in their bases, sometimes entirely devoid of it. 



2180. O. caryophyllacea Sm. (= O. Galii Duby). (Kirchner, ' Flora v. 

 Stuttgart,' pp. 642-3.) — The nectar-yielding flowers of this species possess a 

 clove-like (Kirchner) or benzoloid (Kerner) odour. The corolla-tube is some- 

 what bent, and widens out gradually from base to mouth. The lower lip is 

 trilobed, and provided with four folds at each side of the middle lobe, inclining 

 inwards against the upper lip. These folds narrow the entrance of the flower to such 

 an extent that a bee visitor, in pushing its head below the upper lip, must touch 

 stigma and anthers. The flowers are homogamous. The large, feebly bilobed 

 stigma projects beyond the anthers, so that it must be first touched by an insect, 

 the next flower visited being therefore cross-pollinated. The four anthers are laterally 

 united, and each lobe is provided with a sharp, stiff, downwardly-directed process. 

 These processes are behind the stigma, and if anything strikes against them the 

 bright-yellow, powdery pollen falls out of the anther-lobes, and is sprinkled on 

 the proboscis or head of the visitor. Automatic self-pollination is excluded. 



2181. O. Rapum-genistae Thuill. ; 2182. O. lutea Baumg. (=0. rubens 

 Wal/r.); 2183. O. alba Steph. (= O. Epithymum DC); 2184. O. gracilis Sm. 

 ( = 0. cruenta BertoL). (Schulz, ' Beitrage,' II, p. 219.) — Schulz noticed perforated 

 flowers of these species at Siegen in Westphalia, at Halle, and at Bozen and 

 Oberbozen (Tyrol). In the last-named species the perforations were made by 

 Bombus terrester Z. 



2185. O. major L. (= O. elatior Sutton). (Knuth, ' D. Bestaubungseinricht. 

 d. Orobancheen.') — So far as mechanism goes the flowers of this species belong to 

 class Hb, but those I observed at Heiligenhafen in Land Oldenburg were without 

 scent or nectar, and of an inconspicuous brown colour. The stigma at first projects 

 beyond the anthers, but is afterwards reached by them, so that automatic self- 

 pollination must take place. 



2186. O. crenata Forsk. (=0. speciosa DOj. (Knuth, 'Bliitenbiol. 

 Herbstbeob.') — This species is indigenous to France and Italy. I was able to study 

 it in the Kiel Botanic Garden, where it was growing as a root-parasite on Vicia 

 Faba L. The large bilobed stigma is situated above the entrance to the curved 

 corolla-tube (2 cm. long), and the four anthers lie behind it in the tube, so that 

 automatic self-pollination is excluded. When one of the larger insects creeps into 

 the flower, it first touches the stigma, and then strikes against the downwardly- 

 directed anther-processes. The first visited flower is self-pollinated as the insect 

 backs out of it, but those subsequently visited will be crossed. 



