606 Pearson . — On the Micro sporangium and Microspore of 
crowded ; they are arranged in about eleven regular parastichies, each 
containing five to seven flowers. These relations obtain in G. Gnemon , 
G. latifolium , G. neglectum , and G. funiculare. In G. Rumphianum the 
number of flowers in each parastichy is smaller. The hairs arise from single 
superficial cells between the insertions of the flowers ; they are particularly 
abundant between the female flowers and the male which stand immediately 
beneath them. The axis of the male flower bears two anthers, except in 
G. Rumphianum , in which there is only one. Of the two perianth leaves 
the upper arises earlier than the lower and overlaps it in aestivation. In 
the young anther there are two hypodermal tapetal layers clearly derived 
by periclinal division from a single layer. 1 After the cessation of division 
in the sporogenous cells, the walls separating them become indistinct and 
finally invisible. The body of the sporangium then consists of £ lediglich 
freie Zellen ohne Cellulosewande mit je einem Kerne 5 ; this is surrounded 
by the two- (sometimes three-) layered tapetum and the epidermis. These 
* freie Zellen ’ are the pollen-mother-cells. A contracted condition of the 
nuclear thread precedes the first division, which is rarely seen ; it is followed 
immediately by a second division resulting in the presence of four free 
microspore nuclei in each mother-cell. At maturity the pollen-sac wall 
consists of a single layer of cells. The cells bordering the transverse line 
of dehiscence are either smaller or larger than the rest, and their contiguous 
walls are so rounded off that the area of contact is small. The presence of 
pores in the exine, as described by Strasburger, is denied ; its surface is 
covered by delicate warty protuberances. Microspores in various stages of 
germination are found in the same sporangium. The first nuclear division 
in the microspore was not seen. One of the nuclei of the binucleate spore 
divides, the spindle in this case being very difficult to see. No more than 
three nuclei were seen in the pollen-grains ; in this condition they appear 
to be mature. On germination the pollen-grain contains only two nuclei. 
No distinct generative cell can be seen in the pollen-grain, but it appears 
in the pollen-tube. 
Lotsy 2 finds three free nuclei in the pollen-grain of G. Gnemon 
before its transference to the ovule. He regards one as vegetative, two as 
generative. He confirms the statement of Karsten that a generative cell 
occurs in the pollen-tube of G. mollucanum. 
Coulter 3 found twelve chromosomes in the heterotypic and homotypic 
divisions in the pollen-mother-cell of Gnetum Gnemon . 
Gnetum africanum is a climbing species occurring spasmodically in 
the dense forests of Central Angola, Gaboon, and the Kameruns. Its 
recorded localities in Angola are about 150 km. from the coast ; they are 
1 Karsten, 1. c., Taf. viii, Fig. 14. 
3 Coulter (’08). 
2 Lotsy (’99). 
