REPRODUCTION. 205 



wholly different, we will not discuss. Neither a supporter of the 

 theory of descent nor any physiologist can at the present time hope 

 to solve the question What changes are necessary in the idioplas- 

 matic structure in order that a microspore which regularly forms 

 motile fertilizing elements may develop a fertilizing tube like that 

 of the pollen -grain? 



The so-called ' ' vegetative ' ' cells which regularly appear in the 

 pollen -grains of conifers are looked upon as evidence in favor of 

 the theory of descent. These pollen-grains are several-celled, but 

 only one cell develops into the pollen-tube. The remaining cells 

 are supposed to be a " rudimentary male prothallium. ' ' The 

 microspore of Selaginella is also several-celled, and has a vegetative 

 cell. Anxious searchers for phylogenetic characters will naturally 

 allow themselves to become blinded by factors apparently in their 

 favor. Even in the present state of our knowledge on the subject 

 I will venture the statement that the contents of the vegetative 

 cells in the pollen-grains of conifers, etc. , serve to nourish the cell 

 which develops into the pollen-tube. According to JUEANYI, one 

 of the vegetative cells contains starch. 1 ELFVING* states that the 

 vegetative cell of Leucoium oestivum is reabsorbed, while its nucleus 

 as well as the nucleus of the reproductive cell is later found in 

 the pollen-tube. Other observations teach that very long cells, 

 such as the laticiferous tubes and the bast-cells, are frequently 

 multinuclear. It must also be remembered that the pollen-grain 

 of conifers requires a long time to reach its destination, hence must 

 have some food-supply. 



In Selaginella, which contains two kinds of spores, the macro- 

 spore separates from the mother-plant before the formation of the 

 archegonia. The germinating macrospore which develops sterile 

 archegonia is not equivalent to the germinating seeds of phanero- 

 gams, but rather to the embryo-sac, which is not adapted to become 

 separated from the mother-plant, hence does not separate, and 

 forms its egg-cell apparatus near the apex, in the most suitable 

 location for fertilization. From the above considerations of re- 

 production we see that that which is physiologically equivalent may 

 differ very widely morphologically. The ripe seed of phanerogams 



1 Pringsheim's Jabrbucber, VIII, 1872. 



2 Studieu ilber die Pollenkoraer, etc., Jeu. Zeitscbrift f. Naturwissenschaft, 

 XIII (new series). 



