Nor does the process end here. The flowering plant is rarely uniaxial--it is nearly always multiaxial. From its primary shoot there grow out secondary shoots of like kind. Though occasionally among Phænogams, and frequently among the higher Cryptogams, the germs of new axes detach themselves under the form of bulbils, and develop separately instead of in connexion with the parent axis; yet in most Phænogams the germ of each new axis maintains its connexion with the parent axis: whence results a group of axes--an aggregate of the fourth order. Every tree, by the production of branch out of branch, shows us this integration repeated over and over again; forming an aggregate having a degree of composition too complex to be any longer defined. * * * * * [NOTE.--A criticism passed on the general argument set forth in the foregoing sections, runs as follows:--“I have already pointed out that the process of evolution by which you believe the Liverworts with a distinct axis and appendages to have been produced from the thalloid forms is not founded on sound evidence either in comparative morphology or development. But even if we admit that such an integration of a proliferously-produced colony might have given rise to the leafy _Jungermanniaceæ_, there are even more weighty objections to the supposition that the same process produced the shoot structures of the flowering plants. In the first place the flowering plant-body is _not homologous with the liverwort plant-body_, since they represent different generations. The liverwort plant-body or _gametophyte_, _i.e._, the generation bearing sexual organs, is homologous with the prothallus of ferns and other Pteridophytes, and in the Flowering Plants with reduced structures contained within the spores (embryo-sac and pollen-grain) but still giving rise to sexual cells. The liverwort spore-capsule and its accessory parts (in fact everything produced from the fertilized egg) is homologous with the sporogonium of the mosses, and, as most botanists think, with the leafy plant-body of Pteridophytes and Phanerogams. This generation is called the _sporophyte_ and from the spores which it produces are developed the gametophytes of the next generation. These generalizations were first established by Hofmeister, and all subsequent work has tended to establish them more firmly. The only doubtful question is (and the doubt is mainly, I think, peculiar to myself, certainly not being shared by the majority of botanists) whether the sporophyte of Mosses and Liverworts is really homologous with that of Pteridophytes and Phanerogams, whether it may not rather be regarded as a parallel development along another line of descent from the Green Algæ.