CYTOLOGY 



33 



typic spindle. In this way the anaphase of the heterotypic division passes 

 directly into the metaphase of the homotypic division. The chromosomes 

 now split longitudinally as in mitosis, the two halves pass to opposite poles, 

 and the subsequent stages follow the same sequence as in ordinary nuclear 

 division, the final result of the whole process being the reformation of 

 four monoploid nuclei. This is usually followed by the formation of four 

 cells, though all may not necessarily survive. These monoploid cells mark 

 the beginning of a new phase in the cytological cycle of the life history in the 

 organism concerned, and they normally function as reproductive cells, 

 beginning also a new generation. Whether they act as non-sexual spores 

 and germinate directly, or whether they function as gametes which only 

 germinate after conjugation, depends on the type of alternation of generations 

 which the organism displays, but in plants the former is universal outside 

 the Thallophyta. 



Chromosome Numbers of Types Described in this Textbook * 



ALGAE 



Chlamydotnonas spp. 

 Spirogyra spp. 

 Pandoritw nioriim 

 Eudorina elegatis 

 Volvox aureus 

 Oedogonium spp. 

 Cladophora glomerata 



20 



24 

 24 



20 

 24 

 38 

 30-32 



Vaucheria terrestris 

 Cutleria midtifida . 

 Dictyota dichotoma 

 Funis serratus 



Batrachospermum moniliforme 

 Polysiphonia violacea 

 Corallina officinalis 



20 



48 

 32 

 32 

 20 

 40 

 48 



FUNGI 



Myxomycetes {most spp.) 

 Plasmodiophora brassicae 

 Mucor hiemalis 

 Cystopus Candida . 

 Sphaerotheca castagnea , 



16 

 16 



4 



24-32 

 8 



Erysiphe communis 

 Rhytisma acerinum 

 Peziza vesiculosa 

 Puccinia graminis 



i6 



8 



16 



4 



Peltigera canina 



LICHENES 



Chara fragilis 



CHAROPHYTA 



48 



Pellia epiphylla 

 Marchantia polymorpha 

 Anthoceros laevis . 



BRYOPHYTA 



16 Mnium hornum 



16 Polytrichum commune 



8 Sphagnum squarrosmn 



12 



12-14 

 40 



Lycopodium clavatum 

 Eqinsetum arvense . 

 Isoetes spp. . 



PTERIDOPHYTA 



28 Psilotum triquetrum 



56-230 } Dryopteris filix mas 



96-104 

 144 

 22 Pteridium aquilinum . 64 



* The diploid number is given in each case. Where the number varies considerably it 

 probably indicates that the higher number is that of a polyploid. 



