CRUCIANELLA 45 
sional exceptions may be found, may be regarded from the 
phylogenetic point of view as a step further removed from the 
condition in Angiosperms in general in which the tendency to form 
cell walls may be regarded as an inheritance from forms in which 
the megaspores are in maturity free bodies. 
Similar failure on the part of the megaspores to form cell walls 
has been reported to occur in Eichhor nia * and in Avena and is 
probably of much wider occurrence than at present supposed. 
Certain authors—Juel, Murbeck and Koernicke especially — 
have recently concentrated attention anew to the constancy and 
significance of these divisions—the tetrad division. In addition to 
the evidence adduced from the character of the nuclear mitoses, 
to which reference is made in another part of this paper, the facts 
which speak for the morphological equivalency of the cells which 
justifies the use of the term megaspores as applied to them have 
been set forth at length by Koernicke.t 
Remarkable as is the regularity with which the megaspore 
mother-cell divisions take place, still more so is the further di- 
vision, in very many instances, of a// the megaspores simultaneously. 
If we regard these as the first embryo-sac divisions, which we are 
justified in doing from a comparative standpoint, we are forced to 
regard the eight resultant nuclei derived from a single megaspore 
mother-cell as representing four embryo-sacs lying tandem. It 
has been determined by actual count that some ovules may thus 
be supplied with a dozen young embryo-sacs. Of these two or 
three of those derived from the megaspores lying adjacent to the 
micropylar canal may commence to develop into functional em- 
bryo-sacs. Only one, however, normally attains full development. 
The very evident physiological as well as morphological equiva- 
lency of the megaspores in this plant irresistibly compels the com- 
parison with the conditions seen in certain heterosporous vascular 
cryptogams, especially with Se/aginel/a, in which the majority of 
the megaspores serve as nutriment for the functional ones. 
* Smith, W. R. A Contribution to the Life History of the Pontederiaceae. Bot. 
98 
Gaz. 15: 1808. 
T Cannon, W. A. HEP ageing Study of the Flower ge rq of the Wild 
cad 
Oat, Avena fatua L. Proc, Cal . Botany, 111. 1: 32 
$ Studien an Embryosack- ی ی تون و‎ d Natur. und Heilk. 
Sens 1901. 
