HARD WICKE 'S S CIENCE- G SSI P. 



73 



GRAPHIC MICROSCOPY. 



By E. T. D. 



No. IV. — Pollen of Mallow. 



OSSIBLY the first 

 use the possessor 

 of a newly - ac- 

 quired microscope 

 applies the instru- 

 ment to is the 

 examination of 

 flowers. Easily- 

 obtained floral en- 

 velopes of plants, 

 arranged for ob- 

 servation without 

 difficulty, offer 

 immediate attrac- 

 tion, and naturally 

 the powdery pol- 

 len-bearing an- 

 thers surmounting 

 their filaments, 

 arranged around 

 the pistil and 

 stigma, soon arrest attention. The charm of 

 colour, form, variety, and strange contrivance, 

 under moderate magnifying power, are easily ob- 

 served, and even an experienced microscopist, with 

 knowledge of the deeper significance of plant de- 

 velopment, finds a pleasure in the contemplation of 

 the general elegance disclosed in the disposition of 

 these organs. 



The flower of the common mallow {Malva syl- 

 vcstris), picked when the anthers are ripe and just 

 opened, discloses a combination of parts (more or less 

 modified in other instances) which may be taken as 

 typical. Here may be seen, on their "conspicuous" 

 filaments or stems, the anthers (the cradle of their 

 production), smothered with microscopic bodies, 

 " free " pollen cells, specks filled with a fine mole- 

 cular substance termed " fovilla," but each containing 

 the element of a fructifying power in its resulting 

 influence beyond comprehension. To meet this con- 

 dition of things is the "stigma," of loose elongated 

 cellular structure, secreting a viscid fluid, which. 

 No. 232. — April 1884. 



accumulating at thebase,'forms the "nectar" of bees. 

 The mode of contact is varied and peculiar ; in the 

 mallow the process may be described in general terms. 

 The anthers, when ripe, burst ; the released grains 

 touch the loose tissues of the stigma, and complete the 

 fructification so far ; the future process is of deeper 

 interest, involving the development of the embryonal 

 vesicles, and the subject then outstrips the range of 

 "popularity," and touches on the domain of physio- 

 logical botany, requiring the most careful dissection, 

 preparation, use of chemical reagents, staining fluids, 

 and the highest powers of the instalment. 



Pollen, or "blossom-dust," varies in different flowers 

 in shape, colour, and markings, distinguishable 

 under the microscope — size and shape in an extra- 

 ordinary degree. It is curious to contemplate that 

 these cellular bodies, dispersed by wind, rain, the 

 agency of insects, and other adventitious aids, keep 

 their separate vitality, integrity, and special quality, 

 the power of their influence being distinctly confined 

 to the exigencies of the plants from which they 

 emanate. Perhaps the most beautiful and perfect 

 specimens are to be found in obscure weeds ; and wild, 

 indigenous plants, the evening primrose {(JLjiothera) 

 for shape, the common musk-plant (Mimuhcs mos- 

 chatiis) for elegant marking, may be taken as typical ; 

 the wild geranium {Pelargonium), the hollyhock 

 {Althcra rosea), and the sedums also afford peculiar 

 forms. Colour is various : red ( Verbascicm), blue 

 {Epilobhim), black (Tulip). 



This subject naturally leads to the strange correla- 

 tion or association of necessity between insects and 

 plants. The scattering or placing of pollen is of all 

 importance in the production of future plants, but it 

 cannot be, nor is it always, effected by wind or rain 

 disturbance ; but in many instances it is partially, 

 and in other cases can only be brought about by the 

 dii-ect mechanical interference caused by insects (the 

 Hymenoptera in particular). In the economy of bee 

 life the collection of pollen is of vital necessity, and 

 in every instance it aids the functions of the plant. 

 The most ordinary observer has watched the industry 



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