944 REPORT — 1900. 



forming secondary xylem and phloem only),wluch seem to me still too vaguely de- 

 fined in our text-books. 



Such a classification would also apply to lower organisms. Indeed, my atten- 

 tion was first drawn to the matter by the observation that some algae and schizo- 

 mycetes appear to be always in the embryonic stage. 



This brings us to a second point. Attention is now always drawn to the 

 differences between the slow dimensional growth of the so-called embryonic tissues 

 of the gTOwing points and the stretching phase which Sachs called to our notice. 

 But it seems to me we ought to recognise that we have two fundamentally 

 different things here. It is, I thinlc, hopeless to restrict the meaning of the word 

 ' growth "(as understood by botanists) only to that mode of dimensional increase by the 

 intersusception of solid particles in the non-vacuolated protoplasm of the true 

 embryonic tissue of an embryo, and which implies a real gain in substance by the 

 assimilation — in the sense of the word employed by animal physiologists — of food- 

 materials. Yet this is real growth. The word 'growth,' as understood by botanists, 

 refers almost exclusively to the possibly totally different dimensional increase 

 implied in the extension of cells under pressure of vacuoles, and, taking into 

 account the respiratory activity which prevails, is attended by loss of substance. 



I would therefore suggest that we should distinguish the assimilatonj (jroivtho? 

 true embryonic tissue from the vacuolar groivth of the. i.e,T:\vQA tissues. This can 

 easily be done now that we are beginning to discard the misleading phrase ' carbon 

 dioxide assimilation ' in favour of some such term as ' photo-synthesis." 



Here, again, clearness is, I think, attained by the change in the consideration of 

 those algaa and schizophytes in which no vacuoles can be detected. It would be 

 absurd to say they do not grow ; but it seems pretty clear that they grow by 

 assimilatory groxoth and not by vacuolar (/rowth or extension. At the same 

 time we must not forget that invisible vacuoles may exist in the meshes of proto- 

 plasm, though even if this be so it is difficult to see how the protoplasm in the 

 trabeculse between grows if not by the intercalation of solid molecular units. 



2. The Behaviour of the Nucleolus during Karyokinesis in the Root 

 Apex of Phaseolus. By Harold Wager, 



From a study of the changes undergone by the nucleolus during karyokinesis 

 In cells of the root apex of Phaseolus multiflorus the following chief results have 

 been obtained. 



1. The nucleolus is the most conspicuous object in the nucleus of the young 

 meristematic cells. The nuclear network forms a delicate peripheral layer only 

 in the resting nucleus. 



2. The nucleolus stains deeply in hasmatoxyhn, the nuclear network slightly ; 

 in safranin and gentian violet the nucleolus stains red, the nuclear network light 

 blue ; in gentian violet the nucleolus often shows a more deeply stained central 

 portion. 



3. In the resting condition of the nucleus the nucleolus is suspended to the 

 delicate nuclear network by delicate filaments. 



4. The nucleolus often shows a vacuolar structure, especially in the stage just 

 previous to division. 



6. In the process of nuclear division the nucleolus first of all becomes irregular 

 in shape, and the nucleolar substance appears to pass, by means of the connecting 

 strands, into the nuclear network, which thereby becomes more prominent. 



6. As the chromosomes are formed the nucleolus disappears, but a portion of 

 the nucleolus is often visible in the equatorial plate. 



7. The chromatic substance of the chromosomes appears to be derived almost 

 entirely from the nucleolus, but a part of the nucleolus may possibly be used up in 

 the formation of the spindle fibres. 



8. As the daughter nuclei are being formed the chromatic substance of the 

 chromosomes runs together into small spheres, which ultimately fuse together to 

 form the single large nucleolus. 



