AROIDEAE 491 



temperature is perceptible at 9 a.m., several hours before the opening of the inflor- 

 escences : the maximum, 40 C, is reached between 6-8.30 p.m. The spadix loses 

 weight considerably during the increase. 



Kraus (Abh. nat. Ges., Halle, xvi, 1884, pp. 35-76) observed that the evolution 

 of heat inside the spathe rises to 40-44-7*' C. in an air temperature of 17-7 C. This 

 increase of temperature usually begins at the tip of the spadix, and spreads thence to 

 its base. The oecological significance of this increase is that it induces the pollen- 

 transferring midges to descend into the warm trap. As the visitors use the tip of the 

 spadix as an alighting-platform, this becomes warm first and most strongly. The 

 increase of temperature only takes place during the first (protogynous) stage of the 

 inflorescence, and ceases when this is over. 



Visitors. The following were recorded by the observers, and for the localities 

 stated. 



Delpino ('Ult. oss.'), 6 Diptera (identified by Rondani) i. Ceratopogon pictellum 

 Rond. ; 2. Chironomus byssinus Schr. ; 3. Drosophila funebris F. ; 4. Limosina 

 pygmaea Zeit. (= L. crassimana Hal.)', 5. Psychoda nervosa Schr. ; 6. P. nervosa 

 Mg. ; Knuth (Capri), numerous minute Diptera, and a staphylinid 4 mm. long. 



2910. A. temattim Thunb. (= PinelHa tuberifera Tenor e). (Breitenbach, Bot. 

 Ztg., Leipzig, xxxvii, 1879, pp. 687-92; Herm. Miiller, 'Fertlsn.,' p. 564.) The 

 inflorescences in this species are protogynous. The pollen of the male flowers falls 

 upon the small imprisoned insects (probably flies) which can then escape by a small 

 opening. 



2911. A. crinitum Ait. (Schnetzler, C.-R. Acad, sci., Paris, Ixxxix, 1879, 

 pp. 508-10,) The flower mechanism of this species resembles that of A. maculatum. 

 Carrion-flies are attracted by a strong smell of putrefying flesh. The smaller visitors 

 cannot escape from the trap, but are held there firmly by sticky hairs and digested 

 by their secretion. 



Arcangeli (Nuovo Giorn. bot. ital., Firenze, xv, 1883) observed flies more 

 particularly as visitors; in one spathe there were 385 Diptera, 107 of them belonging 

 to the species Lucilia caesar L. The upper part of the spathe is bent like a knee, so 

 that only the lower part forms the ' bridal chamber.' The upper part bears closely 

 situated purple-red weel-bristles, directed obliquely downwards. The stigmas are as 

 short-lived as those of Dracunculus vulgaris. 



The plant is therefore adapted for pollination by Diptera. Such crowding of 

 visitors into a single spathe as Arcangeli observed probably does not occur in 

 a natural state ; but in the plants examined was the result of the small number 

 cultivated. This excess of visitors is indeed injurious to the plant, as they injure one 

 another and die in the 'bridal chamber,' only a small number therefore emerging 

 again during the fourth stage of anthesis, 



2912. A. pictum L. Arcangeli (Ric. ist. bot., Pisa, Fasc. i, 1886, pp. 108-9) 

 found 95 insects in one inflorescence in the Pisa Botanic Garden, consisting of 

 86 Borborus (Copromyza) equinus Fall., 3 Aphodius melanostictus Schmidt, an 

 Oxytelus nitidulus Grav., 4 other smaller flies, and one hymenopterid (probably 

 a parasite of Borborus). 



The visitors were plainly attracted by the dark-purple colouring of the spathe 



