ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
205 
BOTANY. 
A. GENERAL, including the Anatomy and Physiology 
of the Phanerogamia. 
a. Anatomy. 
(1) Cell-structure and Protoplasm. 
Centrosomes in Plants.* — Reviewing tlie present state of our know- 
ledge on this subject, M. L. Guignard insists on the improbability that 
these bodies, present in animals and in the lower divisions of the vege- 
table kingdom, should be absent from the higher plants. In animal 
cells the centrosome is regarded as the most important part of the 
centrosphere ; it is a refringent corpuscle, often exceedingly minute. 
The centrosphere itself is composed of a substance which may be differ- 
entiated into two zones — the internal one hyaline, the external granular. 
In cells in a state of repose it is formed of the substance which some 
authors term archoplasm or kinoplasm, to distinguish it from nutritive 
protoplasm or trophoplasm. In this state there is sometimes one, 
sometimes there are two centrosomes, sometimes a considerable number 
lying side by side, constituting what may be called a micro-centre . 
The author then proceeds to point out the variation in the structure 
and form of the centrosome in different families of Tliallophytes : — round 
in the Fucaceae, rod-shaped in the SphacelariaceaB.f In these groups it 
appears never to be surrounded by a sharply differentiated sphere, 
while this is the case in certain Muscineae. From observations made on 
nuclear division in the pollen-mother-cell of Angiosperms (. Nymphsea , 
Nuphar , Limodorum), the author concludes that the formation of multipolar 
spindles, whether normal or accidental, is not a valid argument against 
the existence of dynamic centres in the division of the nucleus. There 
exist in the cytoplasm, at a certain moment, bodies distinct from ordi- 
nary granulations. It is probable that the higher plants are provided 
with differentiated kinetic elements the function of which is the same as 
that of the analogous bodies in animals and in the lower plants. 
Movement of Protoplasm in Ccenocytic Hyphae.J — Mr. J. C. Arthur 
finds the streaming of protoplasm to be a universal phenomenon in 
the hyphao of all Mucoraceae examined, — Mucor Mncedo, M. racemosus , 
Bhizopus nigricans, B. elegans, Phycomyces nitens , Sporidinia Aspergillus, 
Thamnidium elegans, Pilobolus crystallinus. In this streaming movement 
it would appear that all the contents — cytoplasm, microsomes, food- 
bodies, nuclei, vacuoles — participate. There is sometimes an evident 
ectoplastic layer lining the cell-wall which does not take part in the 
movement ; but this is often so thin that it is no longer visible. All 
kinds of granules are borne along in the current. The vacuoles, how- 
ever large, are also swept along ; and, at the right stage of growth for 
movement, the protoplasm is usually highly vacuolated. The movement 
is usually fitful. It does not take place in all the hyphse of an indi- 
vidual plant at the same time, but occurs in some of the main filaments 
* Comptes Rendus, cxxv. (1897) pp. 1148-53; Bot. Gazette, xxv. (1898) 
pp. 158-64. f Cf. this Journal, 1897, pp. 107, 108. 
J Anu. of Bot., xi. (1897) pp. 491-507 (4 figs.). 
