128 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. i-xvf. 



all force. Taking these in the order of their occurrence, 

 the first is that the sexual cells of all plants do not 

 separate themselves from the Ijeginning from the somatic 

 cells. Prohably all the higher plants, the metaphyta, are 

 here referred to, for in many of the lower plants all the 

 cells might be regarded as potentially reproductive, or 

 " sexual." In the higher plants the " sexual cells " do 

 appear at a very early period in the sexual generation. 

 The higher one ascends, the earlier is this epoch ; for in 

 the flowering plants, for instance, the life-span of the 

 sexual generation, the gametophyte, is exceedingly short, 

 and it is concerned solely with the differentiation of, and 

 the provision for, the sexual cells. These latter certainly 

 do not appear as such in the asexual generation or 

 sporophyte, nor is it to be expected that they should. 

 Were they to do so, the sporophyte would lose this 

 character, and become a gametophyte. Moreover, even 

 in the asexual generation, the sporophyte, the morphological 

 continuity is unbroken, for in this the future germ-cells 

 are represented by their direct ancestors, the one or more 

 cells forming the apex.^ 



^ Compare Noll's eloquent testimony in the following : — " The Con- 

 tinuity of the Emhryonic Substance. — The vital capacity of the cells of 

 the functioninc; permanent tissue is always limited in time — mostly, 

 indeed, very closely so. Without limit, on the contrary, and never 

 finding a natural close, the vital power of the embryonic substance 

 is preserved. This it is which forms the growing points of the 

 perennial plants, and from this, as Sachs first demonstrated, the 

 growing points of the sexual progeny are directly derived through 

 the substance of the germ-cells. This embryonic substance does not 

 ^ge ; it produces new passing individuals, but it is permanently 

 preservecl in their progeny : it is always productive, always growing 

 young and increasing. Thousands upon thousands of generations, 

 which have arisen in the course of millions of years, vrere its products, 

 but it lives on in the youngest generations with the power of giving 

 origin to coming millions. The individual organism is transient, but 

 its embryonic substance, which produces the mortal tissues, preserves 

 itself imperishable, everlasting, and constant. Regarded from this 

 standpoint, the difterences in the duration of life between short and 

 long-lived plants, between annual herbs and the thousands of years 

 old giants of the plant-race, appear in another light. Out of the 

 embryonic substance of that lime tree of Neustadt every year new 

 leaves and buds form, but these remain in connection with the dying 

 remains of structures of earlier years. In the annual plant, on the 

 contrary, the embryonic substance separates itself every year in the 

 embryo from the mortal remains, and forming new branches, leaves, 

 and roots, becomes a completely new individual. 



"At the basis of the old and well-known dictum of Harvey, 'omne 



