it>4 
Notes on Recent Literature. 
somes corresponding precisely with those of animal cells; these 
bodies undergo division; they neither occur within the nucleus nor 
arise from the latter ; in somatic cells of root and stem-tip they are 
irregularly scattered but during nuclear division tend to collect at 
the poles of the spindle, whereas in the dividing pollen-mother-cells 
they form a mantle around the spindle but are absent from the 
poles. The most remarkable result however was the transformation 
of the chondriosomes in the root-tip cells into leucoplasts and that of 
those in the stem-tip into chloroplasts, which Lewitsky claimed to 
have demonstrated. In this process the chondriosome swells at 
each end while the middle portion becomes longer and thinner, then 
the substance of the pyriform or spindle-shaped portions loses its 
homogeneity and is differentiated into a darkly-staining outer layer 
and a clear central region, the latter being traversed by fine but 
sharply defined threads. Meanwhile each end has grown in size 
and the two young plastids formed by the disappearance of the 
connecting thread gradually assume the definite characters of 
leucoplasts or chloroplasts by further growth and division. The 
quite young cells at the growing-point contained only chondriosomes, 
but in older cells their number diminished as that of the leuco¬ 
plasts or chloroplasts increased. 
Pensa (1910), who independently came to the same conclusion, 
at first studied the ovaries of various plants, using both the Benda- 
Meves method and the reduced-silver methods of Golgi and Cajal, 
and carefully traced the behaviour of the chondriosomes as well as 
that of the nuclei in successive stages of development. The 
chondriosomes appeared as rounded or ovoid grains which were 
either scattered through the cytoplasm or showed a tendency to 
aggregation at the periphery of the cell or on the other hand 
around the nucleus, and which grew in size as the development of 
the flower-bud proceeded. Frequently, as in Tulipa, these bodies 
had the form of rings or of a network : in other cases they were 
rod-like or filamentous and either straight or curved in various 
ways. He concluded that these bodies give rise to chromatophores, 
and that in fact they represent various stages in the development 
of leucoplasts and chloroplasts, while at the same time they are 
morphologically similar to the chondriosomes of animals. 1 Pensa 
later (1911) admitted that the Benda fixative is not w T ell adapted to 
the study of this subject since it causes disorganisation of the 
stroma of the chloroplast and granular deformations of the included 
starch-grains which then stained deeply with haematoxylin. Pensa 
agreed with Lundegard that certain fixatives (especially those 
with chromic acid) are unsuitable, but contended that the silver 
method is free from this objection and that the structures he 
observed were certainly not artificial. He found that the blackening 
of the plastids with the silver method depended upon the presence 
of chlorophyll but not upon that of starch, and that this reaction 
1 “ Tutte queste formazioni che ho descritto e che si colorana in nero col 
metodo dell’argento ridotto e che somigliano, dal punto di vista morphologico, 
in rnodo cosi perfetto ai mitocondri delle cellule animali sono intimamente 
legate alia formazione dei cloroleuciti o corpo clorofilliani, anzi rappresentano 
le varie fasi di sviluppo dei cloroleuciti stessi. Ii facile convincersene perche i 
cloroleuciti completamente formati si colorano anch’essi in nero o in bruno col 
metodo indicato e si possono seguire i varii stadii di passagio dalle forme pill 
svariate di granuli, di bastoncini, di fllamenti a quelle per le quali e indubbia 
a nature di cloroplasta.”—Pensa (1910), p. 330. 
