April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 359 



right side of the cells derived from the true archesjDorium. 

 That the sections through the ovules are uot oblique, and that 

 we are really dealing with oblique divisions, is proved by fig. 

 4, in which the cell a is showing a diaster with the equatorial 

 plane placed obliquely to the long axis of the cell. The 

 development of the integument from the dermatogen is shown 

 in figs. 2, 4, 9^ 12, 14, 15. The integument grows more 

 vigorously on the superior convex surface of the ovule as 

 compared with the lower concave surface. How the curva- 

 ture of the ovule upon itself causes a compression of the cells 

 of the dermatogen just where the ovule is connected to the 

 mother-axis, and how this same curvature leads to disorgan- 

 isation of the integument between the funicle and the nucel- 

 lus or body of the ovule, may also be gathered from the above 

 figures. This compression and disorganisation proves that 

 the ancestral ovule must have been an erect structure, with 

 an integument surrounding it on all sides; but, that from some 

 cause or other — maybe by the rapid growth of the carpellary 

 leaf, the latter ensheathing the ovule on all sides — the up- 

 ward growth of the ovule was interfered with, and that it 

 thus was forced to grow downwards in the direction of least 

 interference. 



B. The Intermediate Period. 



We have already seen how of several original archesporia 

 only one performs its physiological function of giving rise to 

 a number of sporocytes, and we shall find that of these 

 sporocytes, again, only one will fulfil its physiological function 

 of giving rise to spores. This latter I shall call- — analogously 

 to the terminology applied to the archesporium — the physio- 

 logical sporocyte, while those sporocytes not undergoing 

 further development will be the non-physiological ones. 



It has been pointed out, how, of the sporocytes derived 

 from the archesporium, the one lying next the plerome 

 (figs. 7-9^ ^.aS'.) is the one placed under the most favourable 

 conditions with regard to the supply of food, and how, further, 

 its cell-wall, abutting on the plerome, does not undergo gela- 

 tinisation, — a fact which can be explained on the supposition 

 that the embryo-sac-cell has become parasitic in its habits, 

 and that a swelling of its wall lying next the source of 



