Considerazioni Sopra I Piú Noti Reperti di “Fenomeni Meiotici„ In Tessuti Somatici

RIASSUNTO

L'A. ha preso in esame e revisionato criticamente i più noti reperti di « fenomeni meiotici » in tessuti somatici, sia nel campo animale sia in quello vegetale.

SUMMARY

The author has studied « meiotic phenomena » in somatic tissue. From the available data it is concluded that:

1)	In animal tissues, the phenomena reported for the larval ileum of Culex are, very likely, to be ascribed to mitosis with polychromosomes;
2)	In the tumors in general and in tissues treated with carcinogens, the induced cytological aberrations merit a deeper study, to be based on our present knowledge of endomitosis, mitosis with diplochromosomes, somatic segregation, etc.
3)	In plant tissues, examples of meiotic or meiois-like figures have been reported for tapetal cells, cells of the connective tissue of the anther, in the ovarium and nucellus cells. Almost all of these findings appear as exceptional and not easily controllable facts. The only exception is the case described in Hieracium hoppeanum, in which somatic cells in the nucellus frequently give rise to reduced embryosacs and to normal embryos.
4)	A completely peculiar case, hitherto unique in the literature, is that reported for Sambucus nigra, S. Ebulus and S. racemosa, and probably present in Adoxa moschatellina. In these plants there is a typical somatic tissue (gland cells in the base of the stylar canal) the cells of which constantly undergo typical meiotic phenomena during their evolution.
5)	Phenomena of reduction in chromosome number (formation of haploid nuclei) reported as spontaneous or induced by chemicals (sodium ribonucleate, phosphates) in root tips (HUSKINS and coll., 1947–1949) do not show meiotic appearances (synizesis, diakinesis, etc.). The author believes that they are connected with some possible anomalies of chromosome reproduction, centromere division, or with more or less-inefficient spindle mechanism (C-mitosis).