Cytologie und Befruchtung. 211 



und the heterothallic forms which are dioecious. The hetero- 

 thailic forms are the most usual and Rhizopus nigricans may 

 be taken as a type of them. In the heterothallic forms it has 

 been possible to group together under the more and the less 

 luxuriant strains, all the strains which have been brought under 

 cultivation by the vvriter. These two groups of strains repre- 

 sent the opposite sexes. Consequently the zygospore in these 

 iorms is the result of what cannot be otherwise than a sexual 

 union. In all forms the progametes are the result of contact 

 Irritation and not of any tropism. The writer closes with a 

 note in which he expresses the hope that mycologists will 

 assist him in his further investigation, by sending him cultures 

 of any Mucorineae found producing zygospores. 



H. M. Richards (New York). 



Campbell, D. H., Studies on the Araceae. The Embryo- 

 s a c and Embryo o f Aglaonema and Spathicarpa. i Annais 

 of Botany. Vol. XVII. 1903. p. 665.) 



The results obtained in this investigation are thus summa- 



rised bv the author. 



1. In both Aglaonema and Spathicarpa the pistillate flower 

 consists of a solitary carpel containing a Single basal ovule, 

 probably of axial origin. 



2. The embryo-sac of Aglaonema commutatum shows many 

 deviations from the usual type. These consist first in a varying 

 number of embryo-sacs ranging from 1 to 3. Where two 

 or three are formed, this may be from a division of a 

 common archesporial cell but in some cases it looks as if these 

 originated independently from hypodermal cells. All of these 

 embryo-sacs usually undergo the first nuclear divisions, but 

 probably only one ever becomes fully developed. The second 

 peculiarity is the extraordinary Variation in the number of 

 nuclei in the embryo-sac, and in the character of the structures 

 developed in it. The number of nuclei ranges from 4 to 12, 

 and the polarity is usually but slightly indicated. Multiple 

 nuclear fusions are of common occurrence, and it is often im- 

 possible to be certain which of the structures represent the egg- 

 apparatus, and which the antipodal cells. 



3. In specimens of an undetermined species Dieffenbachia 

 Aglaonema, Hort.), perhaps identical with A. commutatum, the 

 endosperm may arise from the direct division of two nuclei (or 

 possibly a single one) at the base of the sac, without any 

 formation of polar nuclei. 



4. A. pictum does not depart to any marked extent from 

 the usual angiospermous type. The pollen-spore of this species 

 has two generative nuclei. 



5. The embryo of Aglaonema, although reaching a large 

 size, shows little differentiation of its external parts, and its 

 tissues are almost perfectly homogeneous. In the ripe seed 

 it almost completely fills the embryo-sac. The nucellus is 



14* 



