62 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



are shot out in all directions. The fruit of Balsam 

 {Impatiens) is somewhat similar. Catasetum, a re- 

 markable genus of Orchids, has flowers which throw 

 out their pollen-masses at any insect w^hich happens 

 to touch their " antennae." Along these sensitive 

 appendages of the flower the impulse is conveyed 

 to a delicate membrane which retains the pollinia 

 in a state of tension. By the sudden rupture of this 

 membrane the pollinia are thrown out in the direc- 

 tion from which the stimulus comes. A sharp line can 

 hardly be drawn between hygroscopic movements and 

 those due to turgescence. Of the latter, the pepo of 

 Momordica elaterixim furnishes an illustration. This 

 plant is called the squirting-cucumber, because, when 

 the fruit breaks away from its stalk, the seeds, along 

 with the watery contents, are shot out as from a 

 syringe. This result, in so far as it is due to the 

 contraction of the walls of the fruit, is hygroscopic,, 

 but very probably fluid pressure brought about by 

 endosmotic activity has also something to do with 

 it. And the same might be said of those fungi 

 which adopt a similar mode of dispersion. The 

 mortar-fungus {Sphcerobolus stellatus) projects its 

 sporangium very much in the same way that a shell 

 is thrown from a mortar. Here the globular spor- 

 angium, retained by the outer membrane of the 

 peridium, is pressed from behind, till the tension 

 suddenly ruptures the membrane and the sporangium 

 is forcibly expelled. The sporangium of Pilobolus^ 

 another genus not at all closely related to Sphce- 

 robolus, is thrown off by the turgescence of an 

 underlying cell. Among the Ascomycetes, many 

 Pezizce and Sphcerice have their spores forcibly 

 expelled from an aperture at the top of the ascus. 

 In Ascobolus the asci themselves, as its name indi- 

 cates, constitute the projectiles. By means of such 

 artillery many of these fungi bespatter neighbouring 

 plants with their sticky fruits and spores. One of 

 the Gasteromycetes presents a curious analogy to 

 Magnolia. The sporangia of Nidularia hang over 



