Yasui.—On the Life-history of Salvinia natans. 479 
an apical cell, being older than the surrounding cells, and ceasing to divide 
in the early stage of development (Figs. 109, no). I found that two apical 
cells lying rather close to each other are situated at the upper sinus of the 
cotyledon, i.e. at the middle of the base of the inverted triangle. 
The further development of the embryo is described in detail by Prings- 
heim, and I have nothing to add to his statement, as I can only confirm it. 
Summary. 
I. The primary tapetum-cells of both sporangia are formed by division 
of the archesporial cell, and they again divide into one layer of many cells. 
3. The spore-mother-cells are eight in the macrosporangium and sixteen 
in the microsporangium. 
3. The number of chromosomes of the spore-mother-cell is sixteen and 
the reduced number in the spore is eight. 
4. During the reduction-division the tapetum-cells begin to degenerate 
and nourish the spores. 
5. Sixty-four mature spores are formed in a microsporangium, but in 
a macrosporangium only one spore becomes mature. 
6. The male prothallium consists of a large prothallium-cell, a small 
root-cell, two sterile cells and two antheridia, which consist of a wall-cell 
and a central cell. The central cell divides twice, and in each of the four 
cells a spermatozoid is formed. 
7. The statement of Campbell, who denies the presence of a sterile cell 
between the two antheridia and the root-cell, was not confirmed, in agree- 
ment with the investigation of Belajefif. Belajeff was not clear about the 
time of the appearance of the root-cell. It has been determined by the 
present study that the root-cell is formed as a result of the second division 
of the germinating microspore. 
8. The spermatozoid is a spirally coiled body having numerous cilia at 
the anterior end, and a large vesicle at the posterior end. 
9. A blepharoplast, which first appears in the cytoplasm and later 
elongates towards the nucleus, was observed in each sperm-cell. 
10. Three to five archegonia are usually formed in each female prothal- 
lium, and each archegonium consists of one egg-cell, a ventral canal-cell, 
a neck canal-cell with two nuclei, and the neck-cells. 
II. Only one spermatozoid enters into the egg-cell. After the penetra- 
tion of the spermatozoid into the egg-nucleus, there appears in the cavity of 
the latter a nucleolus-like body, derived very likely from the spermatozoid 
and somewhat smaller than the nucleolus. 
13. The four quadrants are clearly distinguishable in the young embryo. 
The development of the root-quadrant ceases at an early stage, and later its 
tissue cannot be distinguished from that of the foot. 
