24-4 TlIK AMERKWX MONTHLY [Sopt., 



prndunlly Imh-ohu' faintly ^[rconisli in tlio centre, rcniaininj? 

 white on tin- liorders <)f tlio irrowinu' jtatohes. As th(^ days «^o 

 l>y ihc |»atclu'S increase and thus grow toward each other linally 

 fusini; at their edges and making one continuons hiyer. The 

 oonitlia are tlms seen to be the agents of dispiM'sah The sjtores 

 can he sown in a cell in Pastenr's lUiid. and the (lfvtli>|>iiiciit 

 waiched from day to day. 



This is hy a jirocess of l)udding as in theyi'ast cell. On tlie 

 surface of the s])ore a small swelling arises (Fig. 5)). This en- 

 larges, it still increases Incoming a thread, it is a young hyi>ha. 

 This, besides elongating, soon gives rise to lateral buds and they 

 elongate and in their turn give rise to new hypiia*. The jtlant 

 thus increases rapidly, each hyjiha l)ecoming tlie fruitful parent 

 of many equally fruitful daughters. As to the rate of the growth, 

 this can be observed if you will select some very young bud in 

 a rapidly growing plant and keep it under continuous obser- 

 vation for an hour or so. A series of drawings should b<' made 

 at intervals of every five minutes to show the different stag's 

 of growth. 



The growing hy)>ha^ of Penicillium are very interesting for de- 

 tailed and minute microscopic study. They require to be ex- 

 amined with a i)Ower of at least 4(X) diameters to show the 

 points now to be mentioned. The}' are bounded by a cell-wall 

 which is composed of a peculiar variety of cellulose. Within this 

 wall can be seen the finely granul ir ))rotoplasm. In the tips of 

 the hypha- the cell-wall is filled itrincipaliy witii the protoplasm, 

 l)Ut in the older parts of the hypiia the })rotoi)lasm isint(;rrupted 

 wiih many "vacuoles." These are spaces in the protoplasm 

 filled with water and ])robal)ly substances in solution. As the 

 mo.st active growth is at the perii)iiery of the circle of the liypha', 

 these being the younger )>ortions, and as the vacuoles an^ not so 

 numerous in them we may ])erliaps conclude that the vacuoles 

 area device for hel|»ing to make bulk without using such an ex- 

 jtensive material as proto])ljism. This is also the case; in the 

 higher plants in which we see tin; cell often very strongly vacuo- 

 lated. 



The hypha' have several modes of branching. Perhaps the 

 commonest is by lateral buds (Fig. 7), which rapidly enlarge 

 and in their turn produce lateral buds. In other cases the hypha 

 forks so that you cannot say that either braiuli is the principal 



