Schneider: the phenomena of symbiosis. 929 



the outer skeletons of animals is perhaps purely accidental 

 unless it can be proven to the contrary that the structural 

 conformations are the result of phylogenetic development. 



Climbing plants are interesting as they mark the beginnings 

 of a highly complicated form of symbiosis. The plants form a 

 close association with their supports, which in most cases are 

 living plants; especially is this the case in the dense jungles 

 of the tropics. Whether these plants cling to their support by 

 means of twining stems, tendrils, suctorial organs or aerial 

 roots, there is more or less absorption of soluble food-sub- 

 stances from the living support and in so far it constitutes a 

 symbiotic relationship. The morphological adaptations favor- 

 ing climbing are however primarily for the purpose of bring- 

 ing the assimilative tissues nearer the sunlight, and away from 

 excessive moisture. The support is necessary in order to en- 

 able them to enter into successful competition with other 

 plants. In "many instances the supporting plant plays the 

 part of a host as in true parasitism (Cuscuta). There is little 

 doubt that the members of the Dodder family were originally 

 climbing plants which took almost their entire nourishment 

 from the soil and air. The contact with the supporting plants 

 gradually developed a wholly parasitic habit. In many of the 

 climbing plants the supporting function predominates while 

 the symbiotic relationship remains practically zero. This is 

 especially true of the large thick-stemmed climbers of the 

 tropics. 



Highly interesting though little understood are the fre- 

 quently occurring neoformations in animals, such as tumors 

 (lipoma, asteoma, sarcoma, carcinoma, etc.,) and cysts of 

 various kinds. Although the origin and true nature of the 

 structures is not well understood, yet they shall receive men- 

 tion here since they partake of the nature of symbionts. It is 

 generally believed that these growths are neoformations aris- 

 ing from the development of dormant embryonic cells. They 

 are foreign to the body in which they live as true parasites, 

 greatly sapping vitality or even destroying life. Various 

 theories have been advanced as to the nature of these growths 

 but none have thus far proven tenable. It is however hoped 

 that the investigations of the near future will give more satis- 

 factory results. 



In conclusion we shall mention a few symbioid phenomena 

 from the insect world and show how they are gradually con- 

 veited into undoubted symbioses. Different species of wasps 



