21 
MacDougal. — Symbiotic Saprophytism . 
by as many as four or five colourless septate hyphae in each. 
The epidermis of the older parts of the roots show signs 
of disintegration, although no complete exfoliation occurs 
in the two or three years of the life of the organ. The 
exodermis consists of very large muriform elements with 
thin walls which are empty for the most part unless traversed 
by hyphae. The cortex consists of about ten layers of ovoid 
cylindrical cells of varying size. The outer layers contain 
more or less starch, and hyphae which form a small number 
of convolutions and branch near the nuclei. Passing inward, 
the convolutions and branching increases in density, until 
in the medio-cortex they form spindle-shaped masses with 
a roughened integument quite similar in all respects to the 
vesicles described elsewhere. The gradually increasing size 
and density of these structures from the loosely woven clumps 
of the outer cortex to the agglomerated masses in the^ medio- 
cortex, demonstrates beyond all question the absorptive 
character of these structures, and also the fact that these 
organs are not in any sense homologous with or analogous to 
the ‘ sporangioles ’ of non-orchidaceous species as indicated 
by Janse ( 16 , p. 150). The clumps of neighbouring cells 
are connected by means of numerous hyphae : fifteen or even 
twenty may be seen in a single plane leading away from one 
clump. The clumps in this case are very large, occupying 
in some instances as much as a half of the volume of the cell, 
and slightly separated from the nucleus by a clear space. 
The influence of the presence of the clumps upon the nucleus 
is very marked : in all cells in which this formation occurs 
the nucleus is two to four times larger than the normal, 
and is densely granular. The form is modified in such 
manner that the nucleus resembles an oblong sac tapering to 
a point at one pole perhaps. In many instances the nucleus 
is curved : in others a constriction is to be seen which 
occasionally has been carried so far as cause an undeniable 
fragmentation of the nucleus into two or perhaps three portions, 
separated by a clear space : the fragments are* equally hyper- 
chromatic. The enlargement of the nucleus in the roots 
