104 



PRINCIPLES OF PLANT-TERATOLOGY. 



its equipment of both scale-leaves and needles. In 

 Sciachpitys the axis has become entirely suppressed. 



The rhizophore of Selaginella is an organ occurring 

 either on the upper or lower surface, or both, at the 

 point of branching of the (usually) dorsiventral stem. 

 It elongates into a root-like organ which grows down- 

 ward to the soil on reaching which it emits roots near 

 the apex which fix it in the soil. The question arises : 

 What morphological value has the rhizophore ? It 

 must surely either represent a root, a shoot, or a leaf. 

 For obvious reasons it cannot be a leaf. It is there- 

 fore either a root or a shoot. 



On this point the following has appeared in the e New 

 Phytologist,' vol. ix, pp. 247-249. It "resembles the 

 root of the same plant in the anatomical structure of its 

 vascular parts, for it has a monarch structure of the 

 stele with central protoxylem. Like a root, it is com- 

 pletely devoid of any lateral appendages in the form 

 of foliar organs. Like a typical root it grows down- 

 wards to the soil and absorbs Avater through its tissues 

 in a direction the reverse of that in which it has 

 grown. It produces lateral endogenous roots. These 

 characters are, in my opinion, not sufficient to warrant 

 us placing the organ in the root-category. On the 

 other hand it resembles a stem or shoot in the fact 

 that it arises exogenously from the tissue of the leafy 

 shoot at the region of forking ; but this in itself is not 

 conclusive evidence in favour of its stem-nature, for 

 exogenous roots are known in various plants. But as 

 Bruchmann points out, the definite place of origin of the 

 rhizophores at the place of forking, growing in a plane 

 at right angles to that of the stem-fork, the whole 

 forming a cross-like four-armed branching-system at 

 that point, speaks strongly in favour of these organs 

 being shoots.* The absence of a root-cap is another 



* In some specimens of S. grandis, grown under abnormally moist condi- 

 tions, which were sent by Mr. E,. H. Compton of Cambridge, there occurred 

 tetrachotomously-branching shoots : at the base of the fork of a vegetative 

 shoot, and, in other cases, of a cone, a leafy shoot of (at least in its lower 

 part) radial symmetry arose on both the dorsal and ventral side. 



