KNT0M01MITI IOKFA E OF THE UNITED STATES. 



tion of thick-walled resting spores adapted to withstand successfully l he most unfavorable 

 conditions. These resting spores, which may be cither sexual (zygospores), or asexual 

 (azygospores), finally germinate and produce conidia thai are discharged in the usual 

 fashion and serve to infecl fresh hosts. Such in brief is the general mode of develop- 

 ment in Entomophthoreae; yet it is subject to so many variations and modifications in 

 the different genera and species thai a detailed comparison of them is instructive as well 

 as necessary for a sufficienl understanding of the family. I shall therefore consider each 

 stage among the Empusae in some detail, having first briefly mentioned the more impor- 

 tant points of structure in the remaining genera. These genera are four in number: 

 Completoria, Conidiobolus, Basidiobol/ts and Massospora, the members of which, as al- 

 ready mentioned, are not all cntomogvnous. 



The ijenus Completoria, which, as has been pointed out by Nowakowski and others, 

 should be placed among the Entomophthoreae, was discovered by Lohde (/. c.) in the pro- 

 thalli of ferns and has been subsequently more thoroughly investigated by Leitgeb (I. c). 

 Its presence is indicated by brown spots upon the prothallus within the cells of w hich it 

 exists in the form of short thick hyphae, which spread from cell to cell by means of slen- 

 der projections. The latter penetrate the cell wall, which becomes modified around them 

 into a sheath-like structure, and having thus gained access to an adjoining cell con- 

 tinue their development at its expense. The two usual forms of reproduction, by means 

 of conidia and resting spores, are found in the genus and are of a very simple type. 

 When about to produce conidia the short thick hyphae or hyphal bodies, as they may be 

 termed for convenience, germinate sending up asexually fructifying hyphae or conidio- 

 phores which, after penetrating to the surface of the prothallus, become swollen at their 

 extremities and produce ovoid conidia which are discharged into the air. After their 

 discharge the conidia become pear-shaped, and the basal papilla of attachment to the 

 basidium, or swollen extremity of the conidiophore, is protruded as a hyaline append- 

 age (JSTabel). The conidia germinate and spread the disease by entering other pro- % 

 thalli with which they may come in contact. The resting spores are formed within the 

 cells of the prothallus, and result from the mere contraction of the contents of the hy- 

 phal bodies, which become surrounded by a thick wall. According to Leitgeb, this 

 formation shows no indications whatever of a sexual origin, although his figures do not 

 seem to preclude such a possibility in view of what is at present known of sexual proc- 

 esses in the group. The germination and further development of these resting spores 

 have not as yet been observed. The genus is at present represented by a single species, 

 Completoria complens Lohde, and has been found and cultivated by Leitgeb upon pro- 

 thalli of numerous genera and species. It is at present unknown in this country. From 

 this comparatively simple form we may now pass to the consideration of one somewhat 

 more complicated, which is also parasitic upon another plant, in this instance a thallo- 

 phyte. 



The genus Conidiobolus was accidentally discovered by Brefeld in connection with 

 his researches upon the Tremellini on which it is parasitic; and its discoverer, having 

 obtained spores from cultures in which it had appeared, was enabled by cultivating them 

 in nutritive solutions, to trace its development with the greatest completeness. The co- 

 nidia grow readily in a decoction of horse dung, forming a mass of branched and 

 rarely septate hyphae; which, having nearly exhausted the nutritive solution, become 



