1899] DEVELOPMENT OF THE MICROSPORANGIUM 357 
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was in Convallaria exactly similar to that in Lilium. All the 
stages were especially clear. The + formation, however, began 
insome cases during the early multipolar condition. The pro- 
ves in Potamogeton was probably also normal. 
Nothing new could be determined in regard to the segmenta- 
tion during the second division. It seemed to be absolutely 
impossible to determine in these plants with any degree of 
cetainty whether the division was transverse or longitudinal. 
All the phenomena, however, seemed to indicate a transverse 
‘father than a longitudinal division in both plants. 
The walls of the mother-cells in Potamogeton were thin as in 
Naias and Zannichellia. 
In the microspores of Convallaria the generative nucleus is 
‘Yey chromatic, and is cut off by a distinct wall, but does not 
‘ecome detached from the wall of the spore until just previous 
‘0 the time of passing into the tube. The division of the nucleus 
‘Sprobably in the tube since it was not found within the spore. 
As in Convallaria, so also in Potamogeton the generative cell is 
tut off very early, but in the latter plant the two sperm cells are 
‘mediately formed. The two male nuclei are inclosed each 
Within its own cell wall, but they both still remain attached to 
& wall of the spore. The two-celled body then passes down 
‘te tube and even into the egg without separation of the two 
‘ils. The spindles in each case are very small and the chromo- 
Somes very minute, 
Corner, University. 
EXPLANATION OF PLATES XXIV-XXV. 
: PLATE XXIV. Convallarta majalis L, 
tr 4 '. One of the angles of a young anther in cross-section, showing the 
‘ * cells derived from the primary hypodermal cell; the two inner are 
eB “S archesporial cells ; the third will form part of the tapetum. 
Ee fig, : : ; : 
as 2. An anther cell at a later stage; the two archesporial cells in jig. 
oo 
tls at Vided several times forming a small mass of tissue; the row of wall 
— ‘op is probably equivalent to that in fig. 7, the tapetum is not yet 
