: 
: 
- “aay 5. Longitudinal section of young ovule with archesporial cell. 
1898] LIFE HISTORY OF THE PONTEDERIACEH 335 
changes of environment. It seems, therefore, that the gameto- 
phyte characters cannot be of much value in assisting us to 
trace phylogenetic relationships among the angiosperms. 
The irregularities which have been pointed cut in Eichhornia 
may be correlated with its enormous power of vegetative repro- 
duction. It has been propagated for years, without apparent 
loss of vitality, in the greenhouses and parks of Chicago, solely 
by this method; and no doubt this is its chief means of increase 
in the rivers of Florida and South America, where it has become 
aserious hindrance to navigation. The variations in the mega- 
Spore series are interesting, since they suggest how the megaspore 
of Lilium may have arisen from a type which had normally a 
fapetum and four megaspore mother cells. Let the change in 
Eichhornia go but a step further, let the nuclei which fail to 
form cells about themselves cease altogether to appear, and we 
should have a primary sporogenous cell passing without division 
ag anembryo sac. Loss of the tapetum, as apparently occurs 
in Hemerocallis fulva by the same process (see the figures in 
Angiospermen una Gymnospermen) , would result in the well-known 
habit of Lilium, where the archesporial cell develops directly 
mto the embryo sac. 
THE University oF CHICAGO. 
EXPLANATION OF PLATES XIX AND XX. 
The plates have been reduced to ten twenty-sevenths of their original size. 
magnifications given are those of the original drawings. 
PLATE XIX. 
Eichhornia crassipes. 
Fic. 1. Longitudinal section of young ovary showing placenta. * she 
Fig. 2, Cross section of an ovary of the same age as fig. I. X 125+ 
ss 3. One of the placente of fig. 2. X 1300. eS 
* 4. Cross section of an older ovary. The cross indicates t 
°vule which is shown in fig. 5. X 125. 
he position 
x 
