NOTES ON RECENT RESEARCH. 



687 



into a strong branching herb, sustaining masses of aerial foliage from 

 enlarged stems floating horizontally on the surface. 



As the floating mat is formed the conditions begin to become xero- 

 philous. Such plants as Clethra alnifolia, Azalea viscosa, Vaccinium 

 corymbosum, Ilex verticillata, Myrica Gale and cerifera, &c, rapidly 

 transform the floating mat into a swamp thicket. 



Though these plants belong to different families, they all agree in 

 having alternate, simple, lanceolate, nearly entire and smooth leaves. 



Decodon passes away before the shrubs, and in due time seedlings of 

 trees appear. 



As these trees grow, often wholly Chamcecyparis, the shrubs are over- 

 topped and give place to them, and the series enters a final cycle as a 

 Chamcecyparis swamp. 



In receding the pond fills up from the' circumference to the centre. 

 In other cases it is reversed, an island forms in the middle and leaves a 

 narrow belt of open water about the edge of the pond. The ditches, 

 though well defined, are quite shallow, yet free from vegetation. 



It was observed that formations of this character w r ere only found in 

 wooded districts. In treeless districts the ponds fill up from the margin. 



The ditch is always widest where the most material is washed in. 



The character of the materials gave the clue. Only fallen leaves and 

 other organic matter are washed into the pond, so that young plants 

 which might start around the edge are constantly smothered. 



The islands themselves are floating on from 2 to 3 metres of water. 



After the island becomes fixed the ditch fills but very slowly. Even 

 after the central area has been occupied by trees, it often may still be 

 plainly traced. — G. H. 



Dipodascus. ' 



Dipodascus, Cell-contents, Fertilisation and Spore Forma- 

 tion in. By H. 0. Juel (Flora, xci. pp. 47-55, t. 7, 8 ; 1902).— 

 Dipodascus albidus is a small mould first found on decaying vegetable 

 matter in Ecuador by Lagerheim, and remarkable for its gigantic ascus 

 containing numerous spores supported by two " legs " (whence its name), 

 the basal parts of two unequal conjugating hyphae, of which the upper 

 coalesced lips have grown up to form it. Juel has rediscovered it on 

 Birch-trunks at Falun, in Sweden, associated with Fusaria, obtained pure 

 culture, and studied its cytology by modern methods. The hyphae are 

 septate ; the chambers, of unequal size, are apocytial, with numerous 

 minute nuclei (2 /i)' in the cytoplasm, which is mostly parietal. The 

 gametes are short terminal, equal, filled with cytoplasm and multi- 

 nucleate ; on their union the protoplasm from the one (" pollinode ") 

 passes into the other (" carpogone "), which grows out into the " ascus." 

 In the fertilised carpogone, among many unchanged nuclei is seen a much 

 larger one (4 from the figures). This is probably derived from the 

 fusion of at least two nuclei. Successive divisions of this zygote nucleus 

 result in the formation of a large number, which for a time become 

 undistinguishable from the vegetative nuclei. However, when the ascus 

 has attained its final size and form it contains two kinds of nuclei, the 

 one homogeneous, more numerous than the others, which are vesicular 



