54 PART I. MORPHOLOGY. 



1G 



dehiscence of the sporangium. In some cases the wall of the 

 sporangium simply degenerates ; in other cases there is a special 

 mechanism, sometimes very elaborate, for its dehiscence. In a few 

 cases the whole sporangium falls off from the parent plant, e.g. the 

 microsporangia and macrosporangia of Salviniacese ; here the 

 spores never become free from the wall of the sporangium, but 

 germinate inside it. 



(b) The Sporophore. Beginning with the lower plants, a well- 

 marked asexual spore-producing organ is to be found in many 

 Fungi, where it represents, in fact, the shoot of the body, and is 

 a specialized, erect-growing branch of the mycelium. It may be 

 simple (e.g. Mucor, Peronospora, Eurotium) or compound (Agaricus). 



The sporophyte of the Bryophyta affords a good example of a 

 highly specialised sporophore in an organism the shoot of which 

 is not differentiated into stem and leaf. The entire shoot of the 

 sporophyte constitutes the sporophore, which consists (except in 

 Riccia) of a longer or shorter stalk (seta\ bearing a terminal cap- 

 sule (theca) of more or less complex structure. 



In the majority of the higher plants, in which the shoot of the 

 sporophyte is differentiated into stem and leaf, there are well- 

 marked sporophores (see Fig. 27). The sporophore may be the 

 terminal portion of the primary shoot or of a branch ; or it may 

 be an entire branch. It is commonly known, among Phanerogams, 

 as the inflorescence, but there is no reason for confining the use of 

 this term to this group of plants. The sporophore or inflorescence 

 is characterised by its limited growth in length, and can usually 

 be distinguished from a vegetative shoot by peculiarity of form, 

 and, when they are present, by the nature of its leaves. 



The distinction of an inflorescence from a vegetative shoot is easy when 

 the former is an entire branch borne latterly on the latter ; but when 

 a monopodial vegetative shoot terminates in an inflorescence, the tran- 

 sition from the one region to the other is so gradual, that it is difficult to 

 determine where the one begins and the other ends. 



The sporophore may be simple, or it may be branched, and it 

 then affords some of the most striking examples of the various 

 branch-systems (see p. 18). When the branch-system is such that 

 there is a well-defined main axis, this is termed the rhachis, of 

 the inflorescence. The rhachis and the branches of the inflorescence 

 are commonly elongated and cylindrical, or flattened, or prismatic 

 in form ; but they are in many cases dilated at the apex into a 

 flattened, depressed or conical receptacle, as in the Composite, etc. 



