278 TEANSACTIONS AND PROCEEDINGS OF THE [Sess. Lix, 



motlicr-ccll, where the reduction of these to one-half has 

 been found to occur. 



I may be allowed to offer a few remarks on this broad 

 conclusion — first, as regards the position of the second 

 critical point in the spore-mother-cell ; secondly, as regards 

 the possible bearings of apogamous and aposporous develop- 

 ments upon this question ; and, thirdly, upon the theory of 

 the process of reduction. 



The critical point of reduction having been now localised 

 in the spore-mother-cells, these appear in a more important 

 light than hitherto. In recent years, when tracing the 

 development of spore-producing members, the attention has 

 been more definitely fixed on the archesporium and the 

 spore ; attempts were made to strictly localise and define 

 the former, while the latter was recognised as bearing the 

 importance of a separate detachable body, which served as 

 the apparent starting-point of the new generation. Now, 

 however, the physiological interest will certainly centre itself 

 upon the spore-mother-cells, as being those in which the 

 essential physiological change, as evidenced by the micro- 

 scopic details, is actually effected ; they, as Strasburger 

 states, initiate the new sexual generation. He goes on, 

 however, to assert that : " Consequently the presence or 

 absence of a well defined archesporium is not a matter to 

 which importance should be attached. For the arche- 

 sporium is merely the merismatic tissue from which the 

 spore-mother-cells are derived, a tissue which is frequently, 

 but by no means necessarily, differentiated from the 

 surrounding tissues at an early stage ; so that its differ- 

 entiation cannot be of fundamental importance." 



From the physiological point of view, I am prepared to 

 subscribe to this statement ; but from the morphological 

 side, it cannot be allowed that the details of origin of the 

 tissues which give rise to the spore-mother-cells are 

 unimportant. That tissue may be found, and, as I have 

 shown at length elsewhere, is found to be various in its 

 origin. It is not uniformly referable in all archegoniate 

 plants to any one layer of cells; its lateral limits are also 

 very variable, even in species of the same genus {Lyco- 

 podium). But notwithstanding this, we, who maintain that 

 spore-production was the first function of the sporophyte, 



