164 PHILOSOPHICAL NOTES ON 



mainly the water that surrounds them. It is only as the cellular 

 mass grew, and became more complex, and much more so after it 

 emerged from a water into an air medium, that a circulatory and 

 stiffening system (fibro-vascular) became a matter of life and 

 death to the plant in its struggles in this new medium. In its 

 transference from an aquatic to a land existence, water, with 

 minerals in solution, icas still a necessity to it, but this had to be 

 sucked up from the soil, and forced into distant parts, surrounded 

 by air instead of water, for the nourishment of the whole colony. 

 The higher plants have not only a system for circulating fluids, 

 but also a system for air and transpiration, all three being func- 

 tionally identical with the blood, lung, and perspiratory systems of 

 animals. 



If the roots of Thallophytes act as roots, whether they are 

 made up of simple cells, or of these, plus a complicated vascular 

 system, as in the higher plants, we are not justified in giving them 

 any other morphological position than that of roots. The distinc- 

 tion between vascular and non-vascular plants seems very unim- 

 portant, for after all the fibro-vascular bundles are nothing but 

 tissues of cells further modified to suit a higher or more complex 

 development of a plant. We surely call carpels all those parts of 

 plants which hold a certain physiological position, whether they 

 be dry as in the pea, or pulpy, as in the plum. We never think 

 of saying the carpel is not a carpel because it is dry, or because it 

 is pulpy. 



Authors have insisted so much on the distinct natures of crypto- 

 gams and phjenogams, and have impressed us so much regarding 

 the total separation of cellular from vascular plants (M. J. Berkeley 

 insisted on it), that we have unconsciously acquired a repugnance 

 to consider them in any way related. Yet reflection must teach 

 us that these apparently essential differences are after all of trivial 

 importance, from a morphological point of view. 



On evolutionary principles, I repeat, we must admit that all 

 land plants, whether cellular or vascular, descended, with modifica- 

 tion, from water plants, the higher representatives of which are 

 the seaweeds of to-day. 



In his " Outlines of Structural Botany " (p. 13), Asa Gray says, 

 " Roots are naked, not producing as they grow, either leaves or 

 " any organs homologous with leaves. They commonly branch 



