BOTANY — BLAKESI^EE. 



137 



(2) The germinatiou of the zygospores of the homothallic species Sporo- 

 dinia is pure homothallic. 



(3) In the germination of the zygospores of the heterothallic species 

 Mucor vmcedo the segregation of sex is completed at some time before the 

 formation of sporangial spores, and all the spores in a given germ sporan- 

 gium are of the same strain, either (-f) or (— ). 



(4) In the germination of the heterothallic species Phycomyces iiitens a 

 segregation of sex may take place at the formation of spores in the germ 

 sporangia, but is only partial. 



(5) In addition to ( + ) and ( — ) heterothallic spores, spores are formed 

 which give rise to homothallic mycelia characterized by a production of 

 spirallj' coiled aerial outgrowths termed pseudophores and the occasional 

 formation of homothallic zygospores. 



(6) The sexual character in these homothallic mycelia is unstable, and 

 in their sporangia a segregation again takes place and (+), ( — ), and homo- 

 thallic spores are produced. (Annales Mycologici, iv, pp. 1-28, pi. 1,2 text 

 figs., 1906.) 



The investigation of the distribution in nature of the sexual strains of the 

 common bread mold {Rhizopus yiigricans) has been extended. (Science, 

 n. s., XXIV, pp. 118-122, July 27, 1906.) 



The results obtained from a study of zygospore germinations in the 

 Mucorineae have led to an investigation of the sexual condition in the 

 sporophyte of Bryophytes. (Botanical Gazette, xlii, pp. 161-178, fol. vi, 

 3 text figs., September, 1906.) For one form {Marchantia polymorpha) it has 

 been definitely determined that a single capsule contains both male and female 

 spores. The exact point in the development of the capsule at which the 

 segregation of sex takes place has not as yet been determined. 



A study of the influence of the composition of the substratum upon the 

 sexual reproduction has been begun and is still in progress. The forms 

 under investigation are included in the following list of species, arranged 

 according to the type of their sexual reproduction: 



Homothallic 



1. Sporodinia grandis. 



2. Spinellus fusiger. 



3. 4. Miicors I and II. 



Heterogamic. 



5. Zygorhynchus Moelleri. 



6. Zygorhynchus heterogamus. 



7. Dicranophora. 



Heterothallic 

 I. Mucor Mucedo. 

 2-7. Mucors III to VIII. 



8. Rhizopus nigricans. 



9. Phycomyces nitens. 



10. Circinella umbellata. 



11. Cunninghamella echinulata. 



12. Absidia caerulea. 



13. Absidia repens. 



14. Absidia sp. 



15. Helicostylum. 



16. Syncephalastrum. 



17. Mucor N, n. gen. 



