Spencer. — On the Fresh-water Algse of New Zealand. 289 



shades of green, from dark olive to emerald, of red, and of blue, from purple 

 to sky blue, which we find in the Algae, are very much the prevailing tints of 

 the leaves and flowers of aerial plants. And again the reddish and yellow- 

 ish brown hues of some Batrachospermea, Lynghyce., Desmids and Diatoms, 

 correspond closely with the shades assumed by the leaves of trees, shrubs, 

 and herbs, after they have lost their summer verdure, and to which is due 

 the picturesqueness of their autumnal foliage. Many Confervoids, which 

 when young have green endrochrome, assume in more adult age a yellowish 

 or brownish hue, and the analogy between this change and that which 

 occurs in the leaves of the oak, the ash, the elm, and other trees, is at least 

 both striking and suggestive. 



Many Alg® exhibit colours which cannot be referred to autumnal 

 influences, or to the effects of age. The prevailing tints among some of the 

 VolvocinecB and Oscillatorieoi have strong points of resemblance with those of 

 the flowers of phanerogamous plants. In the latter the diversities of colour 

 appear to be connected in some way (of which various explanations have 

 been advanced) with the multiplication of the plant, and so we find that the 

 flowers are the parts which are most liable to variations of colouration. On 

 the other hand, in these simple organisms there is no division into stem, 

 leaves, and flowers, almost every portion is concerned in the process of 

 reproduction — each filament or frond represents a perfect herb, shrub, or 

 tree, and every sporiferous cell is the analogue of a flower. In the ph^no- 

 gamic class the floral colours are useful as attractions to insects of various 

 kinds, which, visiting them for food, carry away the pollen to other flowers, 

 and so conduce to their fertihzation. Although, so far as I am aware, no 

 observations have been made on the subject, is it not something more than 

 possible that the multitudes of Infusoria, Rotatoria, Paramecia, etc., which 

 we continually meet with seeking their food amongst the Algse, may assist 

 in the same way as insects in conveying antheridial spores from one plant 

 to another ; and that the varying colours of the filaments may be attractive 

 to them as those of flowers are to insects ; and that thus may be repro- 

 duced in the subaqueous world some of those phenomena with which we are 

 familiar in the aerial ? Should future observation verify this conjecture we 

 shall see amongst the Algse the exact analogue of the entomophilous fertili- 

 zation of flowers, and also be able to understand why the various and 

 beautiful tints they exhibit are, to a certain though much less extent, 

 reproduced ia the filaments and fronds of the fresh-water Alg^. 



In submerged vegetation anemophilous fertilization is of course out of 

 the question, yet even here a substitute appears to have been afforded by 

 the provision of cilia to the androspores and zoospores, to enable them to 

 perform the requisite movements through the water which is their home, 



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