T.ULr.-EXTENSION IN DECIDUOUS ANDINE AMAEYLLIDS, 957 



With Habranthus and Chlidanthus much variation will be found in 

 the shapes of the bulbs : some will have buried themselves more than 

 others, some not appreciably. Seasons also appear to influence the burying 

 propensities of these latter plants. There are writers who place much 

 importance upon the power of the roots to clasp large stones &c, and by 

 their growth draw down the bulb through the soil. 



It is evident to me, however, that it is not necessary, in the cases of 

 the plants with which I am dealing, to have recourse to this theory. The 

 yearly growth downwards and laterally of the lower part of the bulb and 

 the yearly death of the upper part account (mite satisfactorily for all the 

 facts that have been noted concerning them. 



The fact that I selected a hybrid Ismene to draw from was because it 

 happened to present at the time a typical instance of growth ; not more 

 so, however, than either parent exhibits at the same season. 



A great part of the Andine regions are situated in zones of " dry and 

 wet seasons." In many cases the soil is easily disintegrated and the 

 gradients very steep. 



On such steep hillsides the heavy and sudden rains falling on desic- 

 cated soil cause great detrition, and any bulb lying on the surface is liable 

 to be washed away. By establishing themselves at a deeper level some 

 immunity from such accidents is attained. The bulbs also avoid the 

 extremes of surface temperature both in summer and winter, the attacks 

 of hungry animals, and countless other chances to which surface bulbs 

 must be exposed, not to mention the possibility of being started into 

 growth by any slight showers of rain during the dry season. 



Possibly there may be other advantages gained by these self-burying 

 plants. 



