296 Lawson . — The Gametophytes and Embryo of the 
become very numerous before the suspensors elongate (Lawson, *07). In 
this latter case, however, the work of the suspensors in carrying the embryo 
into the endosperm is supplemented by a penetrating cap formed from the 
tip cells of the embryo. 
The further development of the embryo in Libocedrus agrees in all 
essential details with that which I have described for Cryptomeria (Lawson, 
’04), and closely resembles the account given by Land (’ 02 ) in the case of 
Thuja. Fig. 36 shows an embryo of Libocedrus with the middle tier of 
suspensor cells considerably elongated, and a group of embryo cells proper 
at the tip. The nuclei of the rosette may also be seen in the cytoplasm 
of the archegonium above. Fig. 37 represents a still later stage in the 
development of the suspensors. 
Summary and Conclusion. 
From investigations on the pollen of Taxoditim , Cryptomeria , Thuja , 
Libocedrus , Chamaecyparis , Cupressus , and Juniper us, it seems that the 
microspores of the Cupressineae are characterized by the absence of vestigial 
prothallial cells or of nuclei representing such cells. 
The mature microspore consists of two cells, containing respectively 
the generative and tube-nuclei. 
With the exception of Cupressus and Juniperus , the first division of 
the microspore, which gives rise to the generative and tube-nuclei, takes 
place before pollination. 
By the time the pollen-tube has penetrated the nucellar tissue the 
generative nucleus enlarges and divides. As a result of this division the 
body-cell and stalk-nucleus are organized. 
The growth of the pollen-tube is almost in a straight line towards the 
archegonial chamber, and as it advances the body-cell and stalk- and 
tube-nuclei are always found at the tip. 
When the archegonial chamber has been reached the body-cell divides, 
giving rise to two large male cells of equal size. 
The case reported by Juel for Cupressus Goweniatta , where the body- 
cell gives rise to a cell complex, is regarded as an abnormality. 
The number of megaspore mother-cells formed may vary from one to 
three, each of which divides twice. Only one of the resulting megaspores 
germinates. 
The presence of a tapetum surrounding the megaspore seems to be 
characteristic of the group, but it varies considerably as to the extent of its 
development in the different genera studied. 
The functioning megaspore first enlarges, and this is followed by rapid 
free nuclear division. A number of vacuoles now make their appearance, 
but as the spore enlarges these flow together, forming a very large central 
