Telangium ( Ccilymmatothcca ') showing Structure. 175 
if we conjecture that in another Fern the sister sporangia, which were 
already adherent, were retained as a sterile envelope ? 
Turning to the Angiosperms, the modification and abortion of flowers 
in an inflorescence to construct the biologically interesting ‘ flag apparatus ’ 
is exceedingly common. The peripheral flowers in the capitulum of the 
Cynareae , in the thyrsus of Viburnum Optilus and Hydrangea , are among 
the most familiar examples. In Muscari comosum (var. racemosissimum ) 
a very remarkable modification follows the sterilization of the central 
flowers. In Rhus cotinus De Candolle noted an increased growth of 
trichomes on the pedicels of the sterile flowers, and it has hence become a 
classical. example of what he meant by the expression £ correlation of growth.’ 
Passing from flower to sporophyll we have no need to mention any 
of the innumerable instances of the change from stamen to sheathing organ 
which occurs commonly in Ranunculaceae, Scitamineae, &c. In Salvia we 
find that half the anther is sterilized to provide the lever which is to assist 
in the process of cross-fertilization. If a part of a sporophyll can be steri- 
lized and adapted for an accessory function, why should not some members 
of a synangium ? 
Summary of evidence in support of the view that a seed is a synangium 
in which the peripheral sporangia are sterilized and specialized as an inner 
integument : — 
1. Ontogeny. It is shown that wholly independent testimony is borne 
to the fact that in the most primitive of existing Spermophyta, the 
Cycadaceae, a correspondence obtains both in position and development 
between the microsporangial sorus and the seed. 
2. Phylogeny. General considerations would lead us to expect 
comparable characters in the microsporangial sorus and the primitive seed. 
A synangium is the only form of microsporangial sorus so far known 
among the Cycadofilices, and it is found also in Cycadeoidea. 
A special case is cited of sterilized sporangia in the tufted sori of 
Botryopteris. 
3- Suggestions of sporangial origin in the inner integument of 
primitive seeds 
1. It is frequently compartmental. 
2. Each compartment contains large thin-walled cells as contrasted 
with the firmer peripheral layers. 
3. The peripheral wall is constructed of the same characteristic layers 
as are met with in many synangia. 
4. The form of the base and apex of each compartment is often very 
similar to those of members of a synangium. 
5. In some cases there is considerable freedom between the constituent 
compartments whose apices form the so-called tentacles around the micro- 
pyle. 
