42 MacDougal. — Symbiotic Saprophy tis m . 
results in the degeneration of the organ invested by the 
Fungus. The degeneration of roots may amount to a reduc- 
tion to a rudimentary condition, in which instance the Fungus 
is next associated with the stem, a state of affairs to be found 
in some holosaprophytes. Again, the degeneration might 
result from the modification of some other organ. 
It is evident that species of seed-forming plants receiving 
a portion of their food from fungal symbionts, are in a condi- 
tion to undergo much more rapid alteration or development 
than typical autophytes, because in addition to the influence 
of the ordinary environmental factors, the constantly in- 
creasing amount of complex food available has a tendency 
to set other forces in action which result in the degeneration 
of the absorbing organs, the chlorophyll-apparatus, and the 
transpiratory surfaces. Calypso and Aplectrum are of especial 
interest in this connexion, since these species afford still 
further opportunity for variation in the presence of the 
Fungus in a state of transit into a non-absorbing organ. 
Any cause which injures or lessens the supply of food avail- 
able from the absorbing organs, or from the storage-tissues, 
will result in the outward and external development of the 
mycelium in transit, and an accompanying adaptation of 
the non-absorbing organ or offset into a coralloid mycorhiza, 
a fact which has been demonstrated experimentally by the 
writer. Aplectrum exhibits such variations that the descen- 
dants of the individuals now in existence may be divisible 
into three groups: viz, a form with ectotropic mycorhiza 
connected with the roots of Oaks and Maples ; a second form 
with coralloid absorbing organs resembling Corallorhiza ; and 
a third approximately similar to the type now prevalent. 
The second mode of variation seems to be more firmly fixed 
in Calypso , so that great differences are found in the indi- 
viduals now composing the species. 
The variation of the root and shoot as saprophytism in- 
creases shows the greatest diversity, and categorical distinc- 
tions of degree based on anatomical characters are not to be 
relied upon. This is especially apparent when saprophytes 
