154 DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



as monosporous sporangia completely filled by the spore, and most comparable with the 

 sporangiola of the Thamnidieae. These interpretations, which are not in accordance 

 with the facts, have evidently arisen from a perception of the truth, that all the gonidial 

 formations in question are homologous, coupled with the erroneous notion that 

 homologous spores must necessarily originate by exactly the same mode of cell- 

 formation. We naturally gain nothing more from such interpretations in this case 

 than in others of older date which were noticed above on page 116. The homologies 

 are brought out quite simply in our case, as has been shown above, without these 

 artificial helps ; and conversely the case before us shows with special distinctness that 

 members and cells may be homologous, though all the facts observed with regard to 

 them do not belong exactly to one and the same category of the scheme of cell- 

 formation which is accepted at the time. 



SECTION XLIV. Accessory gonidia. In a number of species, in Sporo- 

 dinia grandis for example, Brefeld's Mucor Mucedo, Rhizopus nigricans and 

 Chaetocladium, the cycle of forms is exhausted by the appearance of the members 

 which have now been described; but in other species gonidial formations occur 

 in addition to the typical ones, some of which by their form and structure are 

 eminently characteristic of species and genera. It would seem that they are always 

 found on starved or old mycelia, but the conditions of their formation have not been 

 in every case clearly ascertained. It would be difficult to find any other general 

 name for them than the one here chosen. Many of them have been called by Van 

 Tieghem chlamydospores and stylospores, others gemmae, &c. It will be most 

 convenient to choose a suitable name for each case as it presents itself. 



Characteristic accessory gonidia are the acrogonidia of Mortierella and some 

 species of Syncephalis. They are solitary and acrogenously abjointed on the 

 summit of slender cylindrical branchlets of the mycelium, and are spherical in 

 shape and usually of considerable size in Mortierella (as much as 20 \i or more 

 in diameter), but small in Syncephalis (6 /*) ; they have a thick episporium with 

 its surface marked with warts or spikes in a manner characteristic of the different 

 species, and they emit germ-tubes which may develope into the normal mycelium. 

 They are formed in Mortierella on erect branches of the mycelium which are either 

 isolated or are united into small umbels; in the species of Syncephalis from short 

 stalks which are arranged in dense racemes springing at right angles from a fusiform 

 swollen portion of a mycelial filament. A very remarkable instance of the formation 

 of accessory gonidia is that described by Cunningham in his genus Choanephora, 

 in which the. heads of basidia mentioned above must, from the mode of their 

 occurrence on the normally developed mycelium, be certainly regarded as the typical 

 gonidiophores, though the germination of the zygospores has not yet been observed, 

 and cannot therefore confirm this view. But erect simple sporophores make their 

 appearance on old and starved mycelia by the side of meagre heads of basidia, and 

 form at their summit a spherical mucor-sporangium having a warted outer wall, a 

 slightly convex basal wall, and containing a number of ellipsoid smooth-walled 

 spores, which can germinate and produce a normal mycelium. 



Another form of accessory gonidia is known under the name of gemmae or 

 brood-cells. Their ordinary mode of production is that short pieces of a mycelial 

 tube or gonidiophore, which is rich in protoplasm, become delimited by transverse 

 walls to form cylindrical or nearly spherical or ovoid or pear-shaped or similarly 



