8.] 



CHAPTER II. SPECIAL MORPHOLOGY OF THE MEMBERS. 



37 



rhewhorled leaf-rudiments are raised up by the intercalary growth 



of their common base (Fig. 21 



A, r), and come to be merely 



lappets on the rim of a tube 



(Fig. 21 J5). This explanation 



applies also to perfoliate ancl 



connate leaves (see Fig. 29). 



The union brought about in 

 either of these ways may affect 

 members developed at the same 

 level, or members developed at 

 different levels ; in the former 

 oase the term cohesion is used ; 

 in the latter, the term adhesion. 

 Examples of the former are 

 afforded by gamopetalous corol- 

 las, syncarpous ovaries, etc. ; 

 and of the latter by epipetalous FIG> 21< _ Flower of Petunia . A very 



stamens, by leaves adhering to young (x50); B mature (nat. size); lc the 



the shoots borne in their axils f^ v the lin al0 ^ ^ ^ e f J* 



has been removed ; v the tube; I the lobes 

 ilS in the Lime, etc. or teeth of the corolla. 



CHAPTER II. 



THE SPECIAL MORPHOLOGY OF THE MEMBERS. 

 A. VEGETATIVE ORGANS. 



8. The Thallus. Among those plants in which an alter- 

 nation of generations is not known to occur, the body is a thallus 

 in the lower Fungi {e.g. Schizomycetes, Saccharomycetes, etc.), 

 find in many Algce (e.g. Cyanophycese, some Chlorophyceas, such 

 as Volvox, Desmids, Confervoideae ; some Phasophyceas, such as 

 Ectocarpus, Sphacelaria, etc.). 



Among those plants in which alternation of generations is 

 known to occur, the body may be a thallus in one or both genera- 

 tions ; it is, for instance, a thallus in both generations in some 

 Algas (e.g. Coleochsete, some Rhodophycece), and in Riccia among 

 the Hepaticae : the gametophyte is a thallus in some Algae, in 

 nil the Hepaticae except the foliose Jungermanniaceoa, in most 

 Vascular Cryptogams, and in all Phanerogams : the sporophyte 

 is a thallus in all Rhodophycere ; and in some Phanerogams, as 



