SUMMARY AND CONCLUSIONS 63 
The appearance of a pluricellular archesporium may by no 
means be considered as primitive. It has been shown by several 
workers to occur in widely separated families,* and with certainty 
may be said to have no phylogenetic significance. On the con- 
trary, the meaning is purely physiological, and such conditions 
have arisen in various forms in response to similar conditions. 
When present they offer favorable nutritive conditions for the 
chosen embryo-sac. This view comports at least with the case of 
Alchemilla as interpreted by Murbeck (/. c.) The archesporial 
tissue not directly concerned in the formation of the embryo-sac 
takes activity or passively a nutritive rôle. If their rôle is passive 
they gradually disintegrate, and are absorbed. This appears to 
be the case in the Galieae, Diodia teres and Richardsonia. In the 
Diodia Virginica they grow chiefly in length and arrange them- 
selves asa transporting tissue. As such they connect the embryo- 
sac with the vascular supply of the ovule, and persist for a 
considerable period after fertilization. In Houstonia the subsid- 
lary megaspore mother-cells appear to persist till about the time 
the embryo commences to develop, and undergo regular and con- 
stant changes in size and form. These changes indicate their 
physiological importance. 
5. The embryo-sac cell behaves in two ways. In Houstonia 
and Richardsonia it develops in situ. Inthe Ga/zeae and in Diodia 
it moves forward out of its original position, breaking through the 
nucellar capping cells, and passing along the micropylar canal. Its 
passage is intercellular, and its action is so far analogous to the 
movement of the pollen tube, as described by Murbeck and myself. 
As it moves it derives nutriment from the disintegrating cells 
adjacent to it. The disintegration is such as to suggest very 
strongly the secretion of an enzyme by the embyro-sac. 
The embryo-sac presents some remarkable features as regards 
the antipodal cells. These, in the GaZeae, with the possible ex- 
ception of one species of Asperula, are three in number, one of 
which is very much elongated. The free end of this cell is plunged 
into the mass of disintegrating megaspores and absorbs the same. 
The physiological importance of all the antipodals is indicated by 
*For full citation of the literature see the papers of Murbeck and Koernicke 
D 
