1905.] Development of the Ascocarp q/Humaria granulata. 361 



Davis (12) has criticised such a terminology in the case of Phragmidhtm, 

 and objects to the use of the terms fertilization or sexual process being applied 

 to any union in which the fusion is not between the regular male and female 

 cells. He would class these irregular processes under the head of asexual 

 fusions. 



It is true that a fusion in which the special sexual cells do not both take 

 part cannot, from a purely morphological point of view, be a sexual process. 

 When, however, it is considered that in some of these irregular fusions one of 

 the sexual cells actually takes part, and also that they are of very special 

 nature, being directly related in the phylogeny of the group to the ordinary 

 sexual process, in fact, replacing that process in the life history, they can 

 hardly be satisfactorily relegated to a class of asexual unions, where they are 

 herded with processes most of which have not been shown to have any 

 connection with true sexual fusions.* If on strict morphological grounds 

 these fusions are separated from true sexual processes they should obviously 

 be made a class apart, quite distinct from the asexual unions.f 



It is doubtful, however, whether a purely morphological test of a sexual 

 process (syngamy) is desirable when we consider that the process is essentially 

 a physiological one and that primitively it occurs between vegetative cells 

 (e.g., Spirogyra, some Protozoa). Further, these irregular processes show no 

 characters for which a parallel cannot be found in other accepted sexual 

 processes ; for in the simplest cases the fusing cells are not differentiated, and 

 in other cases of sexuality the blood-relationship between the fusing cells 

 (e.g., lateral conjugation in Spirogyra, sexuality in Basidiobolus and many 

 Phycomycetes) is apparently as close as in the process under discussion. 



Since, then, these special processes in themselves have no characters which 

 remove them from the class of sexual unions, and since they take place 



* Such as the fusion of nuclei in endosperm cells, and in cells which have been placed 

 under abnormal conditions, the fusion of nuclei in the ascus, the " vegetative 13 cell fusions 

 in the Floridea?, etc. 



t In the present state of our knowledge the cell and nuclear unions among plants would 

 seem to be best divided into four classes : — 



(1) Cell-unions of an ordinary sexual nature : 



(2) Eeduced sexual processes as described above : 



(3) Nuclear unions, such as are found in the teleutospore, basidium, and perhaps those 



of the spores of the Ustilaginea? ; these (at least in the case of some Uredinese 

 and probably in the other cases) are the direct result of sexual, or reduced 

 sexual, processes which exhibit nuclear association without, nuclear fusion : 



(4) Asexual cell and nuclear unions, which are of doubtful or purely vegetative 



nature. 



The third class is of very special nature, and it is not satisfactory to class them, as 

 does Davis, with the asexual unions. 



2 D 2 



