206 COMPENDIUM OF GENERAL BOTANY. 



will at once develop into a leafy plant while the mature macrospore 

 must be fertilized before it can develop into a new plant ; from 

 this it is clear that structures which resemble each other morpho- 

 logically 1 may be totally different physiologically. The names 

 macrospore and microspore, embryo-sac and pollen-grain, should 

 therefore be retained as parallel terms. If one purposely ignores 

 what has just been stated, especially that among vascular crypto- 

 gams the sequence is separation from the mother-plant and sub- 

 sequent fertilization, while the reverse is true of gymnosperms, it 

 can be seen how the advocates of the theory of natural descent can 

 assert that the gymnosperms may be classed with the vascular crypto- 

 gams as well as with the phanerogams, 2 that is, that they are midway 

 between the two great divisions. 



Because of the importance of this subject we will add the fol- 

 lowing statements. 



From what has been said it would be wrong to conclude that a 

 slight change in the behavior of the macrospore would suffice to 

 prove the phylogenetic derivation of gymnosperms from the vascular 

 cryptogams. Let us consider briefly what these changes would be 

 and what changes should not take place. In order that Selaginella 

 may arrive at the cycad-stage the macrospore must not adapt itself 

 to become separated from the mother-plant nor undergo a period 

 of rest until it has been fertilized by the suitably organized micro- 

 spore. After this change had been brought about separation from 

 the mother-plant could follow, and the disposition to undergo a 

 period of rest should now become manifest. In order that the 

 macrospore might remain in union with the mother-plant it must 

 undergo an entirely different mode of development. What slight 

 similarity exists between the Cycas-ovule and the sporangium of 

 Selaginella is evident from GOBEL'S statement that the integument 

 of the Cycas-embryo has no analogue among vascular cryptogams, 

 and therefore he calls it a ' ' neo-f ormation. ' ' This investigator is cer- 



c? 



tainly authority on subjects pertaining to comparative morphology. 

 The macrospores of the Cycas- sporangium are not formed by the 

 mother-cell dividing into four, as in the Selaginella. In regard to 



1 It should be remembered that such morphological similarity or dissimilarity 

 of organs which seem dissimilar or similar physiologically is often only apparent, 

 and not real. TRANS. 



2 SACHS, Vorlesungen, p. 913; GOBEL, Grundzilge der Systematik, p. 1. 



