238 WILLIAM TRELEASE— TWO NEW TERMS : 



of the present communication is to propose the addition of two 

 more to the words of precision of our day. Both of the new 

 terms may be dispensed with, it is true, as they have been thus 

 far, if one be disposed to paraphrase sufficiently, or to avoid refer- 

 ence to the well-known facts that they express ; but these facts are 

 so fundamental to a correct understanding of plant morphology that 

 the latter course can scarcely be looked on as desirable, while the 

 former — as every thinking teacher of the science has discovered — 

 proves far from easy. One of them refers to the one-time division 

 of the Vegetable Kingdom into Thallophytes and Cormophytes, now 

 a question of morphology rather than of taxonomy ; the other, also 

 morphological, to the entities that compose the life cycle of one of 

 the highest plants, whose alternating generations are usually spoken 

 of as sporophyte and gametophyte (or the non-sexual and the 

 sexual generation). 



It is understood in a sense that the characters of genus, family 

 and higher taxonomic groups are to be read into the characters of 

 every species ; but even novices know that this can be done only 

 by reading into these group characters a number, sometimes large, 

 of aberrations and exceptions ; so that the popular idea of a 

 thallophyte, with the body undifferentiated into stem and foliage, 

 is not shaken by the occurrence of very stem-and-leaf-like algse, any 

 more than the popular idea of a cormophyte, with regularly disposed 

 foliage on a supporting axis, is disturbed by seeing that a vegetating 

 Wolffia possesses the simplest thallus configuration, though internally 

 differentiated and in due season flow'ering like other cormophytes. 

 The real difficulty lies in the fact that a more important difference 

 exists between thallophytes and cormophytes, so that when properly 

 defined these groups include respectively plants with the body un- 

 differentiated morphologically ; and plants with the body differ- 

 entiated into root and shoot, the latter usually further differentiated 

 into stem and leaf. These characters at once mark the mosses and 

 liverworts as being neither thallophytes nor cormophytes, for 

 although they possess what may be called stem and leaf they lack a 

 morphological root. This is intensified by the universally under- 

 stood circumstance that it is the sexual or gametophytic generation 



