Miyalce, The development of tiie ganietophyies etc. 19 



The feuiale prothalliuni develops, as in the other ( 'onifers, 

 at first by free cell formation in a parietal layer of protoplasm 

 enclosing the central vacuolo. The division of the free nuclei goes 

 haud in hand with the enlargment of the protoplasmic sac. 



The waU-formation between the nuclei begins about June 

 10—15. The cells then elongate toward the center, and cross- 

 walls are laid down before they meet. 



The filling up of the central vacuole with prothallial tissue 

 proceeds rather ra]iidly. and in about a week after the first wall- 

 forniation the whole megasporic sac is filled with solid tissue. 



The young female prothallium is surrounded by two to four 

 layers of tapetum-cells, whilo in the older stages the tapetum is 

 rednced to a Single layer of cells. In the mature prothallium, the 

 tapetum shows the sign of disOrganization. 



The megaspore-membrane is fairly well developed in the 

 mature prothallium, and consists of two layers. It is thicker to- 

 ward the base of the prothallium. 



The archegonia develop from peripheral cells at the micro- 

 pylar end of the prothaUium. They are arranged in a group, and 

 the entire complex is surrounded by a Single layer of sheath-cells. 

 The number of archegonia in a complex varies usually from thirteen 

 to sixteen. The number of the neck-cells in each archegonium is 

 usually four. 



The archegonial complex has a sterile prothallial tissue at 

 the center and the archegonia are arranged around it completelj^ 

 enclosing the former. The archegonia are also surrounded by a 

 common layer of sheath-cells. 



A ventral canal-nucleus is cut olf just before fertilization, 

 and it, as a rule, soon disintegrates, being usually abseut in the 

 mature egg. The mature egg has a large nucleus situated some- 

 what above the center and a vacuole just below it. 



Fei'tilization occurs about the first week of July. A Single 

 sperm-cell enters the archegonium and its nucleus soon fuses with 

 the egg-nucleus. The fusing nuclei are surrounded by a dense 

 sheath of starch-granules. The outline of the female and male 

 nuclei remains distinct until the fertilized nucleus prepares itself 

 for di Vision. 



The division of the fertilized nucleus takes place at or near 

 the center of the egg. The two segmentation-nuclei then move 

 down toward the base of the archegonium. where the succeeding 

 two free nuclear divisions take place. 



Eight free nuclei arrange themselves in two tiers at the base 

 of the archegonium, and the walls are then formed between them, 

 but the Upper side of the upper tier is left open. The nuclei of 

 the Upper tier now divide. The proembryo consists of thi-ee tiers. 

 of cells, and the middle tier elongates into the suspensors while 

 the Upper tier, which is open above, forms a rossette, and the 

 lower tier develops into the embryo. 



The gametophytes and embryogeny of Cimninghamia shows 

 a close affinity with Tnxodiiim and Cryptomeria, and are distinctly 



2* 



