250 DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



cell-contents develope much fatty matter. The gonidia are formed acrogenously on 

 distinct gonidiophores, or in gonidial receptacles, and may be termed acrogonidia. They 

 are when first matured small thin-walled colourless ellipsoidal cells with a gelatinous 

 outer covering and a small drop of fatty matter in the focus ; in size they are 

 4-5 n in length and 2 n in breadth, and are formed in a variety of ways. 



(a) In specimens grown in a poor solution (containing at most five per cent, of 

 nutrient matter) and kept as dry as possible the poorly developed mycelium produces 

 small slender filiform erect gonidiophores composed of a few cells, which form their 

 acrogonidia successively like heads at their apex, or in whorls beneath the upper end 

 of their subterminal cells (Zopf 's formation of microgonidia). 



(d) Stronger mycelia are developed with a more generous supply of food, and these 

 produce erect tufts of many-celled hyphal branches on which acrogonidia are formed. 

 From 2-12 of these branches grow close together, at first closely parallel to one another, 

 but afterwards diverging at an acute angle, and may be nearly a millimetre in height ; 

 the branches in a tuft are of a nearly uniform height. The lower cells of each hypha 

 are elongated and cylindrical, the upper short, scarcely longer than broad, and from 

 them proceed other branches with short cells usually placed on one side only of 

 the cell from which they spring, and rising in the same direction and to nearly the 

 same height as the primary branch, thus resembling to some extent the tuft of 

 branchlets at the extremity of the gonidiophore of Penicillium. From the short cells 

 of all these tufts of branchlets acrogonidia are abscised, terminal ones at their apex, 

 the rest near their upper bounding wall, and all usually on one side and in the same 

 direction. 



(c) The tufts of gonidiophores formed on the mycelium in the way described under 

 division (b) may be firmly united into a bundle along their whole length, while their 

 other characters remain the same. This bundle is at first nearly cylindrical, but its 

 apex spreads out into the shape of a funnel as the terminal ramifications are being 

 formed which will produce gonidia, and their extremities spread out from one another 

 in a penicillate manner ; the abscision takes place only inside the funnel-shaped 

 enlargement, the outer side remains sterile, and the pointed barren extremities of 

 its hyphae extend with a slight divergence a short distance above the tuft from which the 

 gonidia are abscised. 



(d) The sterile extremities of these hyphae may unite laterally and firmly into a 

 narrowly conical tube open at the top, and grow out far beyond the region which 

 supplies the gonidia ; in other words they form a symphyogenetic gonidial receptacle, 

 a more or less elongated flask-shaped pyenidium. The ventral portion of the flask 

 is the region from which the gonidia are abscised, and Zopf found that the process was 

 always carried on from the cells of the wall which continues to be of one layer, and not 

 from other hyphal branches which project into the interior of the tube. 



(e) Lastly, pyenidia of essentially the same definitive structure as those in (d) only of 

 roundish less elongated form, with a wall that is usually two-layered, may also be 

 formed meristogenetically. 



Intermediate forms are found, as might have been expected, between the formations 

 described above from (c) to (e) inclusively. 



2. The acrogonidia when sown in a dilute (five per cent.) nutrient solution sprout 

 and form successive roundish ellipsoid sprout-cells like those of Saccharomyces 

 Cerevisiae ' if the supply of atmospheric air is restricted ; with free admission of air the 

 sprouts are frequently elongated cylindrical shoots (the ' Chalara-' and Mycoderma- 

 form). 



3. All the parts and forms of the Fungus which have now been described may pass, 

 if the supply of food diminishes slowly, into resting states under a great variety of 

 particular forms, while the cells swell, acquire a brown colour and store up fatty 



1 But thev incite no alcoholic fermentation. 



