112 PHILOSOPHICAL NOTES ON 



ietraspores, which may be looked upon as adumbrations of 

 pollen. Harvey says that the fructification is dispersed through 

 all the cells of the frond. If in imagination we contract this 

 frond to the size of an anther, we can form some conception of 

 the evolution of the stamen. Then in the species of Enteromorpha* 

 we get not only adumbrations of stems, branches, and leaves, and 

 roots, but of hairs and spines. The whole plant may be con- 

 sidered either as a root or a frond. Moreover, we find that certain 

 cells of the frond become specialized as tetraspore bearers, that is, as 

 reproductive organs. As in ferns, we begin to find that only at 

 certain points of the frond are reproductive organs developed, the 

 other cells remain as abortive reproductive cells, or simply 

 vegetative cells. 



It may be interesting here to note that in some of the simplest 

 organisms, such as the Giant micrococcus and Sarcina-micro- 

 coccus,^ the cells group themselves in fours, like the tetraspores of 

 algjs, and the mother-cells of anthers in phfenogams, the four 

 cells contained in each mother-cell of the anther becoming the 

 pollen grains. 



In these simple seaweeds, the whole plant is roots, stem, and 

 branches, in ojie. There is yet no need of any differentiation into 

 root and stem, the whole being surrounded by one medium. All 

 that is needed is an organ of attachment, which enables them to be 

 fixed. In Cladophora Rectangularis,% however, instead of a disk 

 we find a root-like organ of attachment. 



If one would care to follow the development of seaweeds 

 further, so as to obtain a conception of the differentiation into 

 special organs, which characterize the higher land plants, he might, 

 with advantage, glance at the following : — 



Rhodymenia cuneata\ gives an idea of the origin of the sori 

 on ferns. Bostrychia IIarveyi\ will show him where ferns may 

 have got their circinate vernation. Callithamnion formosum^ 

 may give him some idea of what the glands on the teeth of rose 



* " Harvey's Phycologia Brit.," v. 4, pis. 263, 245, 340, 43, 344. 



f Dr. E. Klein's "Micro-organisms and Disease," p. 39. 



X " Harv. Phyc. Brit.," v. 4, pi. 12. 



§ " Harvey's Phycologia Australica," v. 5, pi. 295. 



II „ » pl-292. 



T » » pl-281. 



