68 BOTANICAL GAZETTE [jury 
The plant is of such unusual interest that his results deserve rather ful 
statement. 
resembles that described for Ephedra and Gnetum; and at dehiscence thre 
nuclei are found in the pollen grain, one of which, probably prothallial, disap 
pears before shedding. The single megaspore mother cell forms the usu: 
linear tetrad, the innermost spore functioning. In the germination of the meg 
spore there is abundant free nuclear division, and a strong growth of the sé 
towards the micropyle and into the chalazal region. The formation of 
walls occurs throughout the embryo sac, the cells thus formed often being mul 
nucleate. Each peripheral cell towards the micropyle, containing two to fin 
nuclei, produces a tubular outgrowth which penetrates the nucellar cap like 
pollen tube. As this tube advances the nuclei pass into it, and the in 
traversed before pollination occurs is considerable. These free nuclei are s 
and hence the condition is that of Gnetum. These tube-forming cells have bee 
taken for archegonium initials, but it is evident that the tube is only an e 
of the prothallium containing free sexual nuclei; and hence PEARSON r 
calls it the “ prothallial tube.”’ This is a most satisfactory disposition of a trou 
Some structure; and we find that in the act of fertilization Welwitschia is 
more specialized than is Gnetum. : 
It is to be regretted that the first stages of embryo-formation were not s 
by the material, for the current statements in reference to it are as obscure 
meaningless as have been those in reference to the so-called “archegonium 
tials.”—J, M. C. . 
Mendelism in agriculture —No other single scientific proposition has 
so much interest from agriculturists and breeders as MENDEL’s laws of 
sixteen pairs of characters in wheat, five in rye, thirteen in barley, and 
in oats. A short section is devoted to the technic of crossing, and another 
the importance of establishing stations and properly equipping them for ca’ 
ing on such investigations, ee 
76 TSCHERMAK, E., Die Kreuzung im Dienste der Pflanzenziichtung. 
Deutsche Landw. Gesells. 20: 325-338. 1905. : 
