V.] MOULDS. 31 



transverse partitions, continuous with the walls of the tube, 

 divide it into elongated cells, each of which contains a 

 correspondingly elongated protoplasmic sac, or primordial 

 utricle. The hyphas frequently branch dichotomously; and, in 

 the crust, they are inextricably entangled with one another ; 

 but every hypha, with its branches, is quite distinct from 

 every other. Those aerial hyphaa which are nearest the 

 periphery of the crust end in simple rounded extremities ; but 

 the others terminate in brushes of short branches, and each 

 of these branches, as it grows and elongates, becomes divided 

 by transverse constrictions into a series of rounded spores 

 arranged like a row of beads. The spores formed in this 

 manner are termed conidia. At the free end of each fila- 

 ment of the brush the conidia become very loosely adherent, 

 and constitute the green powdery matter to which re- 

 ference has been made. Examined separately, a conidium 

 is seen to be a spherical body, composed of a transparent 

 sac, enclosing a minute mass of protoplasm, in all essential 

 respects similar to a Torula. If sown in an appropriate 

 medium, as for example Pasteur's solution, with or without 

 sugar, the conidium germinates. Upon from one to four 

 points of its surface an elevation or bulging of the cell- wall 

 and of its contained protoplasm appears. This rapidly in- 

 creases in length, and, continually growing at its free end, 

 gives rise to a hypha, so that the young Penicillium assumes 

 the form of a star, each ray being a hypha. The hypha? 

 elongate, while side branches are developed from them by out- 

 growths of their walls ; and this process is repeated by the 

 branches, until the hyphae proceeding from a single conidium 

 may cover a wide circular area, as a patch of mycelium. 

 When, as is usually the case, many conidia germinate close 

 together, their hyphae' cross one another, interlace, and give 

 rise to a papyraceous crust. After the hyphse have attained 

 a certain length, the protoplasm divides at intervals, and 



