Miscellaneous. 399 



On the Part played by Insects daring the Flowering of Arum 

 crinitum, Ait. By M. B. Schnetzlek. 



The spathe of Arum crinitum diffuses so strong an odour of putrid 

 flesh that the insects which deposit their eggs upon decomposing 

 animal matters are attracted by it. The author found dozens of 

 specimens of Musca Ccesar at the bottom of the spathe : they had 

 deposited their eggs ; and numerous small larva were creeping among 

 the viscous hairs lining the interior of the spathe. Common house- 

 flies and even mites were also caught among these hairs. 



Sir John Lubbock has described the transportation by insects of 

 the pollen of Arum maculatum to the protogynous stigmas of other 

 individuals. Hairs, which are nothing but aborted stamens, are 

 directed from above downwards, and thus facilitate the access of 

 the insect to the lower part of the spathe, which, by means of these 

 hairs, becomes a temporary prison for it. 



In Arum crinitum all the hairs produced by the abortion of the 

 sexual organs are directed from below upwards ; and although they 

 do not present any great obstacle to the access of insects they cer- 

 tainly do not facilitate their entrance. The viscous hairs which 

 line the inner surface of the spathe, however, are directed down- 

 wards, and certainly present an obstacle to the escape of insects 

 from the bottom of the spathe. 



On examining under the microscope the ovaries of Arum crinitum 

 at the time when numerous flies occurred at the bottom of the spathe, 

 the stigma was found ready to receive the pollen, and a few grains 

 of pollen were already there, besides many crystals of oxalate of 

 lime. The stamens, although the anthers were not yet open, con- 

 tained perfectly ripe pollen ; and the least pressure sufficed to make 

 it issue from the anthers. 



All the flies found by the author at the bottom of the spathe 

 were dead. The insects penetrating into this prison do not, there- 

 fore, carry out the pollen which has ripened during their captivity, 

 as described by Lubbock in the case of Arum maculatum ; nor is 

 this the office of their larvae (which soon die of starvation) or of the 

 mites. Of the flies attracted by the fetid odour of the plant some 

 lay their eggs at the bottom of the spathe, and then, being pre- 

 vented from escaping from their prison by the viscous hairs which 

 line its entrance, they die. Others, less pressed to oviposit, are 

 attracted by the glandular hairs which cover the spadix and lead 

 them, like the rungs of a ladder, to the stamens. Here, walking 

 over the anthers, they cause the pollen to escape ; and still ascending 

 the spadix in the direction of the hairs, they fly away to lay their 

 eggs in another spathe, at the bottom of which they deposit upon 

 the stigmas the pollen derived from the stamens of the former plant, 

 and finally die in their turn. 



When the dead flies are examined after the lapse of a few days 

 their chitinous envelope is found dried up ; but this is not the 

 result of simple desiccation, as the insect lies upon a moist sui'face, 

 upon which a portion of the liquid contents of the hairs has 



