44 MacDougaL — Symbiotic Saprophytism. 
8. The Fungus symbiotic with Aplectrum forms endotropic 
mycorhiza with the roots, passing out through the root-hairs 
into the substratum. The Fungus is transmitted to the 
vegetative offspring by entering the offset through the special 
trichomes near the base, traversing its length in response to 
chemotropic stimuli, and descending into the young roots 
directly. No degeneration of the stele occurs, and the storage- 
tissues at either end of the offset are not penetrated. 
9. The acquisition of the habit of symbiotic saprophytism 
renders a group of plants extremely unstable as to specific 
characters. 
10. The penetration of non-absorbent organs by the fungal 
symbiont affords opportunity for the utilization of these 
organs for absorption in case of a diminished supply of food 
from the ordinary sources. 
11. The experimental formation of mycorhizal structures 
from non-absorbent organs penetrated by the symbiotic 
Fungus has been accomplished by the writer. 
12. There are but few constant anatomical characters indi- 
cative of partial or complete saprophytism. The presence 
of a symbiotic Fungus in prothallia, and in root- and stem- 
mycorhiza may be taken as an indication of the use of 
complex foods obtained from without. Lack of chlorophyll is 
the only invariable accompaniment of holosaprophytism, while 
degeneration or alteration of the stele is not always consequent. 
Stomata, usually thought to be lacking in Phanerogams 
destitute of chlorophyll, are present in Epipogium , Aphyl- 
lorchis , Lecanorchis , Cotylanthera , and Pterospora . 
