ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 647 



nodes or whorls, afterwards from the base of the fasciculated ramifica- 

 tions, and very often from the base of the branches, where nutrition 

 is shown by the greater activity, especially of those which bear the 

 fertile glomerules. 



The physiological function of these articulated filaments varies 

 with their age, their structure, and their position on the basal or 

 median portions of the axis. When young they are before all absorptive 

 organs ; as is shown by the fact that if the young plant is immersed 

 in any substance which prevents absorption they disappear, and 

 spring again from a more favourable spot. At a later period, when 

 their walls have become thicker, thq lower ones become organs of 

 fixation, while the upper ones constitute the cortication which adds to 

 the strength of the axis, through the hardening of an interstitial 

 gelatine. 



The apices of the verticillate branchlets present a peculiar 

 appearance. In general, when a vegetable cell with thin walls dies, it 

 first becomes inflated, then bursts and disappears. On detached apices 

 the dead cells undergo a contraction to as little as one-fifth of their 

 original dimensions. 



New Zealand Desmidiese.* — Mr. W. M. Maskell has published a 

 list of the Desmidiese found in New Zealand, containing sixteen 

 genera and sixty species, of which six are new or undescribed, viz. 

 Aptogonum undulatum, Micrasterias ampidlacea, Didymocladon stella, 

 Docidium dilatatum, Triploceras tridentatum, Closterium selenceum ; two 

 species of Ankistrodesmiis could not be identified. 



In justification of the creation of the new species (only one new 

 species of diatom having for several years been described from New 

 Zealand), Mr. Maskell, while recognizing that " the lower forms of 

 life, particularly pond life, seem to be pretty much the same all over 

 the world," justifies the creation of the new species on the following 

 grounds. "Although the actual following out of the process of 

 conjugation may be dif&cult or perhaps impossible, I take it that when 

 on several occasions the process of division is to be observed ; when 

 in such cases the resulting frond is identically similar to other and 

 frequently seen fronds ; when there is also at different times of the 

 year, and perhaps in different years, complete similarity in the speci- 

 mens examined ; and when no trace can be found, in descriptions of 

 species by authors, of fronds having the same characters, — there is at 

 least very strong evidence that the plants under review form a definite 

 species different from the known species. To use Mr. Archer's words,f 

 ' Constantly recurring identical forms must be assumed to be the 

 descendants of similar progenitors.' Moreover, division, as I imagine, 

 can only take place in mature fronds — immature plants could scarcely 

 propagate ; consequently any plant seen in process of division must, 

 if no previous record of its characters can be found, be taken as new. 

 For these reasons I have ventured to set down a few plants as new 

 species, and not merely as varieties." 



* Trans. N. Zealand Inst., 1880, pp. 297-317 (2 pis.). 

 t Quart. Joum. Micr. Sci., ii. (1862) p. 238. 



