90 FUNGI. 



the degeneration of the sporangium, which, by the reduction of its 

 spores to one, has itself become a spore. 



In the genera Thamnidium and Ch&tocladium the gradual diminution of the 

 sporangia, and the reduction of the number of spores can be distinctly followed. 

 In Thamnidium the number of spores is often reduced to one, which is free in 

 the sporangium. In Chatocladium however the sporangia are typically one-spored, 

 the spore is always united with the sporangium, and the two become a single 

 body, the so-called conidium, which is in reality a closed sporangium. How 

 close is the connection between the sporangia and conidia of Thamnidium 

 and Chtftocladium, is seen from the fact that, in the conidial stage of 

 Chatocladium the same whorl-form of branching appears as in the sporangial 

 stages of Thamnidium chtftocladioides, and also, that the conidia of Ch. fresen- 

 ianum throw off the former sporangium-wall (exosporium), while Ch. jonesii 

 germinates without shedding its exosporium. The Phycomycetes have doubt- 

 less sprung from Water-Alges and inherit the sporangia from them. On this 

 supposition, as the Phycomycetes assumed a terrestrial mode of life, the sporangia 

 would become adapted to the distribution of the spores by means of the air, 

 the sporangia would become small, contain dust-like spores, and would 

 eventually become closed-sporangia, i.e. conidia. The conidia are a terrestrial 

 method for the multiplication of Fungi. In the Hemiasci and the Ascomycetes 

 the sporangia are still preserved, but in every instance they are adapted to 

 terrestrial spore-distribution, their spores being set free on the destruction of the 

 sporangium-wall (generally shot out) and distributed through the air. For 

 further examples of spore-distribution see below, p. 91-93. 



The reproduction of Fungi is accomplished not only by spores 

 and conidia, but also sometimes by chlamydospores. These are 

 developed in joints of the hyphae by the aggregation of the proto- 

 plasm into masses which become surrounded by a cell-wall and 

 take on a resting condition in the form of a spore, and are able 

 to germinate and produce carpophores. In the formation of the 

 chlamydospores the hyphaa accumulate reserve materials at the 

 expense of the neighbouring cells ; in the undivided hyphee of the 

 Phycomycetes transverse walls are formed, and finally the chlamy- 

 dospores are set free by the decay of the empty cells connecting 

 them with the mycelium. One must distinguish between oidia 

 and true chlamydospores. The former are merely spore-like cells 

 which are cut off from the ends of hyphae (Figs. 162, 184), and 

 which serve for propagation in the same manner as spores. In 

 Chlamydomucor racemosus the chlamydospores grow out into the 

 air and form differentiated carpophores. In the Autobasidiomy- 

 cetes they only germinate vegetatively, and not with the forma- 

 tion of fructifications. From Chlamydomucor up to the Auto- 

 basidiomycetes the successive development of the fructification, 



